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Clapboard and Lap Board Siding Calculator

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Clapboard and Lap Board Siding Calculator

Find the number of clapboards needed using our siding board calculator. The calculator will also determine the overlap and exposure of each board, find the total number of boards needed, and is perfect for estimating cedar wood siding or Hardie fiber lap siding.

Optionally enter the number of doors and windows to refine your estimate.

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How to Estimate Siding Boards Needed

Cedar wood siding and fiber cement siding are commonly available in a clapboard or lap board style and are often sold by the 12′ board. The boards overlap each other and are only partially exposed to the elements to keep the building water-tight.

Lap boards can have different styles to them, such as a Dutch lap, which has the board cut at an angle to cast a shadow, a beaded lap, which has a decorative channel at the bottom, or the bevel, which is thinner at the top than at the bottom.

Regardless of style, you can estimate the number of boards needed in the same way. Even boards like shiplap, which lock together on the top and bottom, or tongue and groove siding are estimated the same way.

You can find the number of boards needed for a project in a few simple steps.

Get the Total Square Footage

One way of determining how much siding you need is to measure the square footage of the area you are siding. For this, you will need to get the length and width of each section in feet. Multiply these together to get the square footage.

For gable roofs, you can measure the square section to the bottom of the roof edge in the same way. Then get the height and the width of the triangular section. Multiply these together, and divide in half to get the square footage of this section.

If you choose, you can get the square footage of the windows and doors, and subtract them from the total.

Most siding is sold bundled. Some are bundled in squares – 100 sq. ft. – while others may be sold in groups of planks, such as 25 planks. In the latter example, you can find the square footage the planks will cover by multiplying the width and length in inches, and dividing by 144.

For example, a popular size for fiber cement siding planks is 6.25″ x 12′ or 144″. This makes each plank 6.25 square feet. Packaged into groups of 25, each group of 25 will cover 156 sq. ft.

While the planks will overlap one another, their full coverage of the wall won’t necessarily be affected by this. Therefore, going by square footage, adding at least 10% for waste, and rounding to the nearest bundle will generally result in an accurate siding estimate.

Find the Overlap and Exposure of the Board

Board siding is installed from the bottom up, with each board overlapping each other by a small margin. Different materials and styles of siding have varying requirements for the minimum amount of overlap needed to keep the wall water-tight and maximize the durability of the siding.

Often, the minimum amount of overlap is 1″ – 1 1/2“.

The exposure of the board is the amount of the board that is exposed to the elements. This can be found by subtracting the overlap of the boards from the actual board width.

The exposure is what will be used to determine the number of courses needed for the wall, and ultimately to find the number of linear feet of siding needed.

Cedar Board Dimensions

Common cedar board sizes and their maximum exposure.

Nominal Actual Exposure
4″ 3.5″ 2″
6″ 5.5″ 4″
8″ 7.5″ 6″
10″ 9.5″ 8″
12″ 11.5″ 10″
Hardie Fiber Board Dimensions

Common Hardie board sizes and their maximum exposure.

Common Hardie board sizes and their maximum exposure.
Nominal Exposure
5.25″ 4″
6.25″ 5″
7.25″ 6″
8.25″ 7″
9.25″ 8″
12″ 10.75″

These dimensions are for average styles and materials only; refer to the siding manufacturer for exact specifications.

Estimate the Number of Courses of Siding

The number of courses of siding can be found by dividing the height of the wall in inches by the exposure of the board. Use our feet to inches conversion calculator if you know the height of the building in feet.

Siding should be kept 6″ off the ground; you’ll need to account for this when measuring and estimating material.

For example, installing siding with a 4″ exposure on a wall that is 12ft high will take 36 courses of siding.

12′ × 12″ per ft = 144″
144 ÷ 4 = 36

It’s likely that a partial course will be needed if the exposure of the board does not divide evenly into the height of the building. In that case, re-calculate the exposure slightly so that each course is even and the top course does not end up being too short.

For example, installing siding with a 7″ exposure on a wall that is 12ft high will take 20.6 courses of siding. Adjust the exposure of the board to be 6.85″ to end up with an even 21 courses.

12′ × 12″ per ft = 144″
144 ÷ 7 = 20.6
144 ÷ 20.6 = 6.85

Estimate Linear Feet

Estimate the number of linear feet of siding needed by multiplying the width of the wall in feet by the number of courses. Boards are most commonly sold in 12′ lengths, though 16′ and 20′ lengths can often be ordered.

Divide the linear footage by 12′ to find the number of boards needed to cover the wall. If you have a board with a different length, such as 16′ or 20′, you will divide by that number.

For example, installing 21 courses of siding on a 20′ wide wall will require 420 linear feet of siding, or 35 boards.
21 × 20 = 420
420 ÷ 12 = 35

Learn more about how to calculate linear feet. Always order at least 10% extra to account for cuts, breakage, and waste when installing.

How to Estimate Gable Walls

Finding the number of boards needed for the area beneath a gable roof is fairly simple. Simply multiply the height and width of the gable and estimate the linear footage like you would for a rectangle using the width and height.

Divide in half to get the linear footage needed to cover a triangular area.

For example, installing 21 courses of siding on a 20′ wide gable will require 210 linear feet of siding, or 18 boards.

21 × 20 = 420
420 ÷ 2 = 210
210 ÷ 12 = 17.5 – round up to 18

Consider ordering additional material for offcuts needed for the angle. While 10% additional may be fine for the other areas, angle cuts may require as much as 20% for this area to account for the many cuts required.

More Siding Installation Resources

Use our siding squares calculator to estimate vinyl siding square material needed. Our board and batten calculator can estimate board and batten siding materials.

Learn more about the cost of siding installation in your area and find qualified installers near you.

Recommended Siding Resources

Brick Calculator

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Brick Calculator

Calculate how many bricks and bags of mortar you’ll need for a wall or masonry project by entering the wall dimensions and selecting a brick size. Optionally, estimate the cost of materials by adding the price per brick.

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How Many Bricks Do You Need?

Bricks are a versatile building material that come in many sizes, wear ratings, and colors. They are often used for exterior walls, chimneys, and fireplaces, but can also be used to create patios, stairs, or some decorative projects.

Many bricks have three or more holes in the center to reduce the weight, raw materials, and cost, while others are solid, and some may be thinner than average. These latter are known as brick veneers and are common for finishing the exterior of a structure rather than being used for support.

Bricks are commonly made of clay or shale and are kiln-baked. They are often laid in courses or rows and are held in position by laying them in a bed of mortar, which also fills the joints between them.

The type of brick you choose will determine how many you need for a wall because bricks do come in different sizes. The thickness of the mortar bed you use can also vary your material needs, as well as the spacing between the bricks.

This calculator assumes a 3/8” mortar bed.

Calculate how many bricks you need using the calculator above. You’ll also get a cost estimate for materials.

You can also refer to the coverage table below or keep reading to learn how to perform the calculations yourself.

How to Calculate How Many Bricks You Need

A wall built with a standard modular brick will require seven bricks per square foot to complete the project. Projects using different sizes may need more or fewer bricks.

Follow the steps below for an accurate estimate.

Step One: Find the Square Footage of the Wall

Start estimating the number of bricks you’ll need by determining how much area you need to cover in square feet. To do this, measure the width and height of your wall or surface.

Once you’ve measured the wall’s width and height, you can find the area in square footage by multiplying the wall’s width in feet times the wall’s height in feet.

drawing showing how to find the square footage of a wall
You can also choose to measure the wall in inches and make your calculation in inches. Once you’ve multiplied the height and width to get your total square inches, you will convert back to square feet.

Divide square inches by 144 to get the square feet. Always round up to the nearest full measurement.

For example, let’s find the area of a 10′ wide wall that is 8′ high.
area = 10′ × 8′ = 80 sq. ft.
Step Two: Find the Square Footage of Each Brick

After you know the surface area, you need to find the amount of area that each brick will cover.

The easiest way to do that is to find each brick’s area in square inches and then divide by 144 to convert square inches to square feet. Keep in mind that there will also be a 3⁄8” mortar joint between each brick.

For example, let’s find the area of a modular brick measuring 7 5⁄8” wide x 2 1⁄4” high

To get the square footage of a modular brick, add 3⁄8” to each dimension to account for the mortar joint, then use the formula (length × width) ÷ 144 = sq. ft. of the brick.

brick & mortar width = 7 5⁄8 + 3⁄8 = 8
brick & mortar height = 2 1⁄4 + 3⁄8 = 2 5⁄8
brick sq ft = (8 × 2 5⁄8) ÷ 144
brick sq ft = 21 ÷ 144 = .1458

You can also use a square feet calculator to easily find the square footage of your brick.

Step Three: Find How Many Bricks Fill the Wall

You can determine the number of bricks needed to cover your area by dividing the square footage of the area to be covered by the brick’s square footage (wall sq ft ÷ brick sq ft).

For example, let’s find the number of modular bricks needed to cover the 80 sq ft wall from the earlier examples. Use the following formula:
80 ÷ .1458 = 549 bricks

We strongly recommend adding 10% additional material to cover any waste and account for any broken blocks or cuts. If you plan on creating any patterns in the brick, add another 10% waste to the total.

The brick calculator above accounts for partial bricks and cutoffs automatically and may return a different number for your project.

Check out our concrete block calculator to find the number of concrete blocks needed for a project. Concrete blocks, or cinder blocks, are larger than bricks, but the strategy to find the number of bricks to cover a surface can be used to find the number of concrete blocks to cover a surface as well.

How Much Mortar Do You Need?

You can estimate mortar by referring to the coverage rate for the specific mortar used on the project. Mortar is a mixture of cement, sand, and often lime. The type of mortar you will use for your project can vary depending on location, flexibility, and the compressive strength needed. Most mortars used for bricks require one bag of cement per 100-142 bricks, depending on the size.

One bag of cement is needed for every 142 modular, 125 queen, or 100 utility bricks. This estimate assumes using a mortar that needs to be mixed with three parts sand. A 1:3 cement to sand mix will require one cubic yard of sand for every seven bags of mortar.

Pre-mixed bags of mortar are also readily available, and an 80-pound bag of mix will often yield 30-36 bricks. Divide the total number of bricks by 36 to calculate the bags needed. Try our mortar calculator to calculate mortar needs more accurately.

Brick Coverage Table

It is important to note that there are many types of bricks and many sizes as well. See some of the most common brick types and sizes below, along with an estimate of how many you’ll need per square foot (or square meter).

Brick Style Size (D x H x W) Weight Coverage
Inches Millimeters Pounds Kilograms Bricks per Ft² Bricks per M²
Modular 3 5⁄8” x 2 1⁄4” x 7 5⁄8“ 92mm x 57mm x 194mm 4.2 lbs 1.9 kg 7 73
Queen 3 1⁄8” x 2 3⁄4” x 7 5⁄8“ 79mm x 70mm x 194mm 4.1 lbs 1.86 kg 6 73
Closure 3 5⁄8” x 3 5⁄8” x 7 5⁄8“ 92mm x 92mm x 194mm 6.8 lbs 3.1 kg 4.5 48
Standard 3 5⁄8” x 2 1⁄4” x 8″ 92mm x 57mm x 203mm 4.5 lbs 2 kg 6.5 70
Jumbo Standard 3 5⁄8” x 2 3⁄4” x 8″ 92mm x 70mm x 203mm 5.9 lbs 2.7 kg 6 61
King 2 3⁄4” x 2 5⁄8” x 9 5⁄8“ 79mm x 70mm x 244mm 5.6 lbs 2.5 kg 4.5 49
Roman 3 5⁄8” x 1 5⁄8” x 11 5⁄8“ 92mm x 41mm x 295mm 4.7 lbs 2.1 kg 6 64
Norman 3 5⁄8” x 2 1⁄4” x 11 5⁄8“ 92mm x 57mm x 295mm 6.4 lbs 2.9 kg 4.5 49
Utility 3 5⁄8” x 3 5⁄8” x 11 5⁄8“ 92mm x 92mm x 295mm 10.2 lbs 4.6 kg 3 32

Sizes and coverage rates of commonly used bricks.

Recommended Siding Resources

Board and Batten Siding Calculator

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Board and Batten Siding Calculator

Find how many boards, battens, and furring strips are needed to install board and batten siding by entering the dimensions of the building below for a wall or gable. Optionally, refine your estimate by providing the number of doors and windows on the wall or gable.

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How to Estimate Materials for Board and Batten Siding

Board and batten siding is the oldest type of milled siding in the U.S. Board and batten siding has a distinctive look with the boards installed vertically.

Historically, the boards were roughly 12″ wide and 1″ thick, but today, the boards can range from 6″ to 12″ in width, with 10″ to 12″ being the most common. Thin strips of wood known as battens, which are usually 1″ x 1″ are installed over the seams.

Board and batten siding is found in wood, metal, and fiber cement, as well as in some vinyl styles. For vinyl and metal, the boards and battens are not separate from one another, and they are designed to overlap and interconnect. For wood and fiber cement, the pieces are separate and need to be installed over furring strips.

The first step to estimating materials is to measure each wall’s width and height,

Illustration showing the composition of boards, battens, and furring strips that make up board and batten siding.

Estimate Furring Strips for Board and Batten Siding

Most homes are covered in plywood or OSB sheathing prior to siding. If this is the case, you can attach the boards for your new siding directly to the sheathing.

However, some older homes that are not sheathed may require furring strips prior to installing the finished siding. Likewise, if you are creating a rain screen, or if you are using certain types of insulation beneath your siding, you may require furring strips as well.

Furring strips are 2″-3″ boards that are installed horizontally every 18″-24″ on the wall. Since the building’s framing is also installed vertically, the board and batten siding will need to be attached to these strips.

To find the amount of furring strip material needed, first start by calculating the number of rows of furring strips that will need to be installed, which can be found by dividing the height of the building in feet by 2 to find the number of 24″ sections on the building.

Round the number up to the nearest whole number, then add 1 to account for adding a strip along the top or bottom edge.

number of rows = (height in feet ÷ 2) + 1)

If your wall measurements are in inches, then divide by 24 instead of 2.

number of rows = (height in inches ÷ 24) + 1)

To find the linear feet of furring strip material, multiply the width of the wall in feet by the number of rows. Learn more about how to find linear footage.

linear feet = number of rows × wall width in feet

Estimate the Number of Boards and Battens Needed

The boards used in board and batten siding are often 10″-12″, but can be any width of your choosing. The boards are wider than the battens, and the battens are installed on top of the seam between each board.

The battens are thinner than the boards, usually 1″ wide and 1″ thick, though they can be wider as well.

Most board and batten siding will have the boards butted up against one another, with the batten over the seam. This comes from the original installations where the home was not watertight, and there was often no sheathing beneath the siding; the battens helped seal up the walls.

If your material of choice is wood, then the boards should have a 1/2″ gap between them to allow for expansion and prevent buckling. Larger gaps can also be used as needed, but the battens should be 1″ wider than the gap to allow for good coverage.

To find the number of boards needed, you simply need to divide the width of the wall by the width of the board. If you are using a panel installation, such as a steel or vinyl board and batten siding, you need the total width of the panel, which is often one board and batten together, but may be as much as two boards and two battens together.

number of boards = (wall width in inches + board spacing) ÷ (board width in inches + board spacing)

To find the number of battens, simply subtract 1 from the number of boards.

number of battens = number of boards -1

Trim should also be accounted for. At least one board will be needed on either side of the wall at the edges.

number of edge trim boards = 2

Most of the time, you will want your boards, battens, and trim to be whole boards, with no joints in the verticals. Because of this, be sure to order material by the board and find boards that are long enough to cover the wall height, and try to avoid ordering material by the linear foot.

However, many homes may be taller than the planks available. To account for this, and to avoid seams in the vertical siding, a horizontal board is usually run at the top of the section of siding. The second, higher section starts on the top half of the board.

How to Lay Out Board and Batten Siding

There are many ways to lay out your board and batten siding. It is common that your exterior walls may not be evenly divided by the width of the boards. However, most homes do have trim around the edges, which can give you some leeway in how you layout and install the boards.

Getting a wider trim can help fill a space where a board may have needed to be cut to fit. Or, if you need to cut boards to fit the space, you can lay out the boards so that they begin in the center of a wall, and move out evenly to either side.

While you may have cut boards on either end, they will be the same width, and will still provide an even and symmetric installation. If your home is not perfectly square, and has interior corners, sometimes you may want to “bury” a cut piece in an inside corner, where it is less likely to be seen.

In some cases, a board may only need to be trimmed slightly. Making a board on the end of the run 10” when the rest are 12” is unlikely to be very noticeable. A very thin board, however, may be less desirable, in which case, larger trim may be the better choice.

You can use our board and batten layout calculator to perfectly lay out an even spacing between the boards and battens.

Note that this step is not required, it is only necessary when it is desirable to avoid an uneven board width on the final board.

More Siding Installation Resources

If you’re installing vinyl siding or need to estimate the amount of material in squares, our siding square calculator can estimate the squares of material needed to cover a wall. Our clapboard siding calculator can help estimate the amount of material needed for clapboard and lap siding.

Finally, you can get free estimates from local siding professionals in your area to compare costs and find a contractor.

Recommended Siding Resources

Roofing Material Calculator

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Roofing Material Calculator

Calculate your roof’s size and estimate how many bundles of shingles, rolls of felt, and squares of roofing material you need for a new roof. Add the price per square for materials to get an estimated material cost.

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*The average cost of materials for a standard 3-tab shingle is about $100 per square, including shingles, felt paper, and nails.

Roofing Material Estimate:
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How to Estimate the Size of a Roof

If you’re replacing a roof, one of the first considerations you make needs to be the roof’s size so you can accurately estimate project materials.

In the US, roofs are measured in square footage, and roofing contractors typically quote projects based on the size of the roof in squares, which are equal to 100 sq. ft. If your roof measures 2,300 sq. ft, then you would need 23 squares of material.

Consequently, gathering the size of the roof in squares and square footage is the first step.

Keep in mind that there is no correlation between the size or square footage of your home and that of your roof. A 2,000 sq. ft. home may have a simple gable roof, a complex cross-gable roof, or a hipped roof, and each one of these roofs will have a different size to them.

Typically, the more slopes your roof has, the higher the total square footage will be. For example, a gable roof has two slopes, so it needs less material than a Dutch roof, which has three slopes, or a hipped roof, which has four. This is true even if the footprint and size of the home itself are identical in each case.

Find the Area of the Footprint of the Roof

To calculate a roof’s dimensions, you need to measure the roof as if it were flat, then account for roof pitch, calculate square footage, and finally determine how many squares of material are required for the roof.

Keep in mind that you will need to do this for each section of the roof. While the illustration above shows a simple gable roof, a cross gable roof will require you to take the length and width of each individual section, and complex roofs like gambrels and mansards will have two sections of roofing to each side.

The calculator above can handle all of this; simply enter the length, width, and pitch, and it will determine the size of the roof in squares.

Start by measuring the roof’s length and width in feet as you’re standing on the ground. Remember that the length and width need to be found for the roof, not the house, so take into account that the roof overhangs the building.

Then determine the area of the roof as if it were flat. Multiply the length by the width in feet to get the area measurement.

Finding the Total Roof Area

Once the area of the roof’s footprint is known, the overall roof area can be found by accounting for the roof’s pitch. The pitch of the roof is the rise over a 12-inch run.

This means that for every 12 inches horizontally, your roof will rise a specific number of inches. Most roofs will fall between a rise of 4/12 and 8/12, but a gambrel roof will likely have a section that is 20/12 and a section that is 7/12. This can mean that you need to calculate for each area separately.

It’s also important to keep in mind that each section of roofing may have its own pitch. This is true even of gable roofs, which may be what is known as a dual-pitch gable – one side of the roof will have a different pitch than the other side. You will need to calculate each side separately in this case.

Use our roof pitch calculator to find the pitch of your roof.

Next, multiply the footprint of the roof by the multiplier below for your roof pitch to find the overall roof area.

For example, a 4/12 pitch roof that is 100 square feet:

100 × 1.054 = 105.4 sq. ft.
Roof Pitch Area Multipliers

Multipliers for common roof pitches that can be used to find the total area of a roof.

Pitch Multiplier
0/12 1
1/12 1.0035
2/12 1.0138
3/12 1.0308
4/12 1.0541
5/12 1.0833
6/12 1.118
7/12 1.1577
8/12 1.2019
9/12 1.25
10/12 1.3017
11/12 1.3566
12/12 1.4142
Finding the Size of the Roof in Squares

Roofing contractors estimate projects and materials by the square, so it is crucial to find this measurement to estimate the amount of material needed accurately. A square simply refers to a 10′ x 10′ square of roofing. This is simply 100 square feet of roof.

To find the squares, divide the overall roof area by 100 and then round up. For instance, if the roof is 1550 square feet, then it is 16 squares.

How to Estimate Roofing Materials

Although roofing projects are estimated and sold by the square, roofing material is often not sold in 1-square increments.

How Many Bundles of Shingles Will You Need

The average bundle of shingles covers 33.3 sq. ft., so three bundles of shingles are needed per square. Asphalt shingles range in price from about $25 per bundle for a standard 3-tab style to around $50-$75 or more for an upgraded architectural style.

Since transportation is a major cost factor, expect prices to vary by location. A typical bundle of shingles weighs about 75 pounds, while some premium products can weigh over 100 pounds per bundle, so consider delivery of materials.

Typically, only asphalt shingles are sold by the bundle in this way. Roofing shingles can come in other materials, including wood, metal, plastic, and slate, and that each of these materials may be packaged and sold in other ways.

How Many Rolls of Felt Will You Need

Roofing felt is sold by the roll. The average roll of 15-pound roofing felt covers about 400 sq. ft., or 4 squares, while the average roll of 30-pound roofing felt covers about 200 sq. ft. or 2 squares.

Rolls of felt are 36″ wide x 144′ long for 15# and 72′ long for 30#. Consider other underlayment options as needed, such as ice and water shield, rubber, or tar products.

The felt that your roof needs will be dictated by the roofing material. 30-pound felt is the most common and recommended type for most roofs, but a tile roof often requires 50-pound. In addition, new synthetic materials are also available, which are thinner and lighter weight while having superior performance.

Always check to see what is recommended by the manufacturer of the roofing material you are installing, or check with your roofer.

How Many Nails Will You Need

Nails will also be required for most roofing projects. The average 3-tab shingle needs four nails per shingle. High-wind areas and other types of shingles may need more. You’ll typically need 320 nails to install a square of standard 3-tab shingles, assuming four nails per shingle and 80 shingles per square.

However, architectural shingles may require 480 nails per shingle. Materials like tile, slate, and some types of metal roofing may use other fasteners as well.

Standing seam roofs, for example, do not use nails but have hidden fasteners in the seams. Always consult the manufacturer for the material you are choosing to use on your roof for the recommended fasteners and number required per square.

Other Materials

Keep in mind that a drip-edge will be needed to protect the roof’s edge from rot, vents, and other materials such as flashing or caulk. Also, consider that the fascia boards may need to be replaced depending on their condition.

Drip-edge and fascia boards are sold by the linear foot, find the perimeter of your roof in feet to find the length of drip-edge and fascia boards needed.

In addition to accurately estimating materials, it is important to make sure you order extra material when ordering. Account for about 5-10% overage on your project to make sure you have enough material if measurements are a little off or material is wasted or damaged. This is more critical for materials that are special-order or have long lead times.

We recommend getting free roofing estimates to understand material and labor costs and identify other project complexities that could affect the cost.

Other Considerations

There are some other factors to consider when installing a new roof. Learn about the costs of installing a new roof. Many localities require permits and inspections for roofing projects; check with your local inspections office and consult local building codes for more information on the requirements.

Also, consider that removing old materials is often required and will require disposing of a large amount of waste. Plan ahead for this by ordering a dumpster for the project.

Think your home might be due for a new roof? Learn the warning signs that it’s time to replace it before it leaks.

Recommended Roofing Resources

Roof Snow Load Calculator

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Roof Snow Load Calculator

Calculate the snow load on a roof by entering the roof’s dimensions below along with the depth.

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How to Calculate Snow Load

Snow load is the additional weight on a roof structure added by snow and ice buildup on the roof. Calculating the snow load is crucial to determining if the structure can handle the snow’s additional weight.

The ATC has a snow load hazard tool that can help you identify when a snow load presents a hazard to the structure.[1] You can calculate snow load in a few easy steps.

Step One: Calculate the Volume of the Snow on the Roof

The volume of snow on the roof directly relates to how much it will weigh. To find the snow volume, start by measuring the roof’s footprint.

Measure the Roof
We strongly recommend against walking on the roof to take these measurements for obvious safety reasons. Instead, measure the length and width roof from the ground to find the footprint; we’ll account for the pitch later. Keep all measurements in feet to simplify the formulas.

When you have the roof’s length and width as measured from the ground, multiply them together. This will give you the area of the footprint. Alternatively, you can also use a volume calculator to find this measurement.

Account for Roof Pitch
If you measured from the ground and did not measure the roof’s actual dimensions, then it’s time to account for the roof pitch. If you don’t know your roof pitch, then try our roof pitch calculator to find it.

To account for the pitch, you’ll need to multiply the area by the multiplier for the given roof pitch. You can find a list of multipliers on our roofing calculator. The calculator above applies this formula. If the roof is a flat roof, then this step is not needed..

Before moving on, multiply the area by the snow depth in feet to find the volume of snow on the roof.

Step Two: Find the Snow Density

Snow varies in weight depending on the density. Fresh powder weighs much less than wind-packed drifts. Check out our snow weight calculator to find the density of various types of snow.

Step Three: Calculate Snow Load

The final step in calculating the snow load is to multiply the volume of snow on the roof by its density. If you have a density range, then multiply the volume by each part of the range separately to find the minimum and maximum snow load.

You might also be interested in our snow to water volume calculator.

Roof Pitch Calculator

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Roof Pitch Calculator

Calculate roof pitch by entering the rise and run or the angle in degrees. Learn more about measuring roof pitch and the rise and run below.

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How to Calculate Roof Pitch

All homes and buildings have roofs. They may range from flat to very steep, some may have curves, and others may have multiple peaks and valleys. All of these roofs have one thing in common; however, they all have what is known as a pitch. Roof pitch describes the slope, or angle, of the roof.

Even flat roofs have a pitch, albeit a small one, as that slope is required to prevent rain and snow from gathering.

Knowing a roof’s pitch is essential in determining what type of material should be installed on the roof, the appropriate installation method, and how much roofing material you’ll need. It’s also an important factor in cold climates for calculating snow load.

Roof pitch, or slope, is a measure of vertical rise to horizontal run expressed in inches per foot, which is referred to as rise over run.[1] Meaning that the roof is measured 12″ in from the edge in a horizontal line, then measured from this point straight up to where the roof intersects. A roof that rises 6″ vertically for every 12″ horizontally has a 6″ per foot, or a 6 in 12 pitch.

Thus, the pitch is the ratio of the rise in inches to a 12-inch run and is often expressed using a semicolon, for example, 6:12. Sometimes, the pitch is also expressed in fraction form using a fraction with a slash, such as 6/12.

You can measure roof pitch by finding the rise and run or by converting from the angle if it is known. See the chart below for the rise and run values for standard roof pitches.

We’ll cover four methods to calculate roof pitch below.

Method One: Measure From the Roof

One method to find the pitch is to climb on the roof and measure the rise for a 12″ run. You’ll need a level that is 12″ or longer and a tape measure.

On the roof, hold the level perfectly level, and measure the height from the roof to the level 12 inches away from where the level touches the surface; this will be the rise.

For example, if the end of a level is 4″ above the roof at a point 12″ away from where it meets the surface, then the pitch is 4:12.

Method Two: Measure From the Attic

Another method to find the roof pitch is to go into the attic and measure the rise over a 12″ run of the roof rafters, allowing you to find the pitch without going on the roof.

From the attic, hold a level perfectly level and touching a rafter at one end. Measure the distance from the level to the rafter 12 inches away from where the level touches the rafter.[2]

Method Three: Measure the Total Rise and Run

If you know the total height of the peak and the roof’s width, you can also find the pitch with a little math. For example, if the peak is 4 feet and the total roof width is 20 feet, then the total rise is 4 feet (48 inches).

The total run is the distance from the peak to the edge of the roof, which in this case is the total width divided in half, which is equal to 10 feet or 120 inches.

Illustration showing how to find roof pitch by measuring the total rise and total ru, then reducing to a rise over a 12 inch run.
Since the pitch is the rise over a 12-inch run, you can divide the run by 12 to get the multiplier; in this case, 120 ÷ 12 = 10.

Then, divide the rise by the multiplier to get the pitch, e.g. 48 ÷ 10 = 4.8. The pitch of this roof is 4.8:12. The calculator above can handle much of this math.

Method Four: Measure With a Speed Square

You can also use a speed square and level to quickly measure the roof’s pitch. Set the level on the edge of the speed square as shown below, then place the heel of the speed square on a rafter or gable edge of the roof.

Holding the tools level, locate the measurement on the speed square where it meets the rafter’s bottom edge to find the angle of the roof in degrees.

How to Convert Angle in Degrees to Roof Pitch

If you know the roof’s angle in degrees, you can find the roof pitch by converting the angle in degrees to a slope, then finding the rise by multiplying the slope by 12.

First, find the slope by finding the tangent of the degrees, e.g. slope = tan(degrees). Then multiply the slope by 12 to get the rise. You can then express the pitch as inches per foot.

Example: let’s find the pitch for a roof angle of 35°.

slope = tan(35°) = 0.7002
rise = 0.7002 × 12 = 8.4
pitch = 8.4:12

How to Convert Roof Pitch to Degrees

To find the angle of a roof in degrees, convert the pitch to a slope, then convert to degrees by finding the slope’s inverse tangent, or arctangent. First, convert the pitch to a slope.

To do this, simply convert the rise and run as a fraction to a decimal form, e.g. rise/run = rise ÷ run = slope. For a pitch expressed in inches per foot, convert to a fraction first, e.g. a 4 in 12 pitch becomes 4/12, then divide.

Next, find the degrees by finding the slope’s inverse tangent, e.g. degrees = arctan(slope).

For example: let’s find the angle in degrees for a roof with a 4 in 12 pitch.

slope =
4:12 =
4
12
= .333

angle = arctan(.333)
angle = 18.4178°

Standard Roof Pitches

Most roofs have a pitch in the 4:12 to 9:12 range. A pitch over 9:12 is considered a steep-slope roof, between 2:12 and 4:12 is a low-slope roof, and less than 2:12 is a flat roof.[3]

The table below shows standard roof pitches and the equivalent grade and angle in degrees and radians for each.

Pitch Grade (slope) Degrees Radians
1/8:12 1% 0.6° 0.01
1/4:12 2.1% 1.2° 0.02
1/2:12 4.2% 2.4° 0.04
1:12 8.3% 4.8° 0.1
2:12 16.7% 9.5° 0.2
3:12 25% 14° 0.2
4:12 33.3% 18.4° 0.3
5:12 41.7% 22.6° 0.4
6:12 50% 26.6° 0.5
7:12 58.3% 30.3° 0.5
8:12 66.7% 33.7° 0.6
9:12 75% 36.9° 0.6
10:12 83.3% 39.8° 0.7
11:12 91.7% 42.5° 0.7
12:12 100% 45° 0.8
13:12 108.3% 47.3° 0.8
14:12 116.7% 49.4° 0.9
15:12 125% 51.3° 0.9
16:12 133.3% 53.1° 0.9
17:12 141.7% 54.8° 1
18:12 150% 56.3° 1
19:12 158.3% 57.7° 1
20:12 166.7% 59° 1
21:12 175% 60.3° 1.1
22:12 183.3% 61.4° 1.1
23:12 191.7% 62.4° 1.1
24:12 200% 63.4° 1.1

Table showing standard roof pitches and the equivalent grade and angle in degrees and radians.

How Pitch Affects the Cost of Roofing

The pitch of a roof will have a definite impact on the cost to install or replace it. Steeper roofs cost more to install, so bear that in mind when choosing the right pitch for your project.

A low-slope roof might cost 10% more to install than a flat roof, while a steep-slope roof might cost 20-30% more. Roofs with a very steep pitch might cost even more than that to install.

Pitch Variations and Unusual Roofs

Not every roof is going to have a perfect, easy-to-measure angle. Some homes may have two different pitches for the roof.

For example, a dual-pitch gable roof has a different pitch on each side of the home. Gambrel and Mansard roofs are considered dual-angle roofs. The lower part of the roof is actually an extension of your home’s walls. This pitch is not quite vertical, but it is close.

In addition, some Mansard roofs are concave on this lower section, which can make it seem to have a different pitch. Both sections need to have their pitch calculated separately. If the roof is concave, you will need to measure from the interior if possible, as the way the roof curves outward at the bottom will give it the illusion of a less steep pitch than it truly has.

Most Gambrel and Mansard roofs are 20/12 on the front section, with a more standard 7/12 on the upper portion.

In complex roofs, such as cross gables, which may have multiple roof areas, you may need to check the pitch of each one – never assume that each section has the same pitch, as it is common for them to vary.

If you’re considering a new roof, we suggest getting several estimates to learn more about the right pitch for your roof and understand the cost of installation. We also cover more about roof replacement costs in detail in our cost guide.

Frequently Asked Questions

A standard pitch is considered anything between 4/12 and 8/12. Anything below is considered low-slope or flat, while anything above is considered a high pitch.

Anything between 4/12 and 8/12 is usually considered a strong roof pitch. However, if you live in an area with a high snowfall, you may want to consider 9/12 or over, while if you live in an area with high winds, you want to consider 7/12, as this is the strongest pitch against high wind.

A 4/12 roof pitch is equivalent to an 18.4 degree angle.

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Plywood Sheathing Calculator

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Plywood Sheathing Calculator

Estimate how many sheets of 4×8 plywood are needed to sheath a roof, accounting for roof pitch.

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Find How Many Sheets of Plywood You Need to Sheath a Roof

Sheathing adds structure and stability to your roof. The sheath is a layer of plywood – usually sheathing or structural plywood – that is applied to the frame of the roof.

It can be made of different materials, from fir and pine to OSB, and gives a stable surface for your roofing to adhere to. All types of sheathing plywood come in sheets that measure 4′ x 8′ nominally.

To find the amount of plywood needed to cover a roof, start by finding the area of the roof. Once the area is known, divide it by the area of a 4×8 sheet to find how much sheathing is needed.

Find the Area of a Roof

Multiply the length of each section of the roof in feet by the width of the section to find the area for that section in square feet. If you have multiple sections of roof, find the area of each and add them together to find the total area.

If your roof is not flat and you cannot climb to the peak to get accurate width measurements, then you can add a multiplier for the pitch of your roof.

Use our roof pitch calculator to find the pitch of your roof or find the pitch multiplier, then multiply the area of the footprint of your roof by the multiplier to find the actual area.

Alternatively, find the area of your roof using our roofing calculator, which can also estimate shingles and material needed for your project.

If your roof has triangles and other shapes, you’ll need to use a calculator to find the square footage.

Keep in mind that different roof shapes will have different square footages, regardless of the home size. A hipped roof will be nearly twice as large as a gable roof, even if both are on a home of the same square footage.

You will need to get the area of each section of roofing and add them together for the total. This includes dormers, cupolas, valleys, and other architectural features.

For example, if your gable roof is 30 ft by 50 ft on each side, then the area for each side is 1,500 sq ft.

30 × 50 = 1,500 sq ft

Combined, this makes your roof 3,000 sq ft.

Calculate Sheathing Needed

Once you have the size of the roof area, you can divide it by the area of a sheet of plywood to find the number of sheets needed. A 4×8 sheet of plywood is 32 sq ft. So, dividing the area of the roof by 32 will give you the number of sheets needed.

For example, if your roof is 3,000 sq ft, then it will take 94 sheets of plywood to sheath it.
3,000 ÷ 32 = 93.75 sheets

You’ll need to round up to the nearest whole sheet, so in this case, you’ll need 94 sheets.

It’s usually a good idea to get an extra few sheets of plywood when ordering to allow for waste and off-cuts. Small scraps are often unusable to span joists and effectively cover the roof, so extra material will save extra trips to the hardware store.

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Metal Roofing Calculator

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Metal Roofing Calculator

Estimate how many metal roofing panels you need with our panel calculator. Optionally, enter the cost per panel to estimate material costs.

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Material Estimate:

Number of Metal Panels Needed

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Square Footage

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Size in Squares

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Material Cost

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How to Estimate Metal Roofing Sheets and Panels

A metal roof is one of the most durable material options for your home. Metal roofs come in many different styles and materials.

Common types include standing seam roofs, metal shingles, tiles, and metal sheet roofing. Aluminum roofs are the most common, but roofing is also available in terne (tin), copper, steel, and zinc. Each type of metal may be available in a set type or types of roofing.

For example, copper and zinc may be available as rolled roofing, while steel can be found in sheets as well as stone-coated shakes and tiles.

Regardless of the type of metal or style of roofing, all metal roofs are sold and installed by the square, which is equal to 100 sq. ft. When ordering supplies, it is important to estimate materials correctly to allow for an efficient installation process.

Estimating the amount of metal roofing material you need starts with estimating the square footage and number of squares of the roof itself.

Steps to Estimate Metal Roofing

Measure the length and width of each roof section in feet, then multiply together to get the square footage.

For some roofs, this can be simple, but for complex roofs, you may want to hire a roofer to give you a more accurate estimate. Keep in mind that the square footage of your home and of your roof have no correlation.

The more sections a roof has, the more square footage there will be. For example, a hipped roof, which has four sides, will need twice as much material as a gable roof, which has two sides, even if both roofs are installed on identical houses with the same footprint.

If you are unable to crawl on the roof, you can estimate a simple roof by measuring the roof’s footprint and finding its square footage. Multiply the footprint square footage by the multiplier for your roof pitch to find the actual square footage of the roof. Use our roof pitch calculator to find the pitch of your roof.

Roof pitch is expressed as the number of inches the roof rises for every 12 horizontal inches. For example, if your roof rises 5″ for every 12″, then you have a pitch of 5/12.

The most common pitches are 4/12, 6/12, and 8/12. Most metal roofing does need to be installed on a roof with a pitch of 4/12 or greater, although some types may be used on lower pitches.

Use the following table to find the multiplier for your roof’s pitch. Multiply the estimated square footage by the multiplier to get a more accurate estimate.

Multipliers for common roof pitches that can be used to find the total area of a roof.

Pitch Multiplier
0/12 1
1/12 1.0035
2/12 1.0138
3/12 1.0308
4/12 1.0541
5/12 1.0833
6/12 1.118
7/12 1.1577
8/12 1.2019
9/12 1.25
10/12 1.3017
11/12 1.3566
12/12 1.4142

For more complex roofs with many peaks and sections, find the square footage of each roof section and add them all together to find the total square footage. In most cases, you will want to add about 10% to the total for waste. You may also want to have some material left over after the roof is installed.

This will allow you to have the material on hand in case of needed repairs down the road. Because roofing materials and colors can change or be discontinued, having extra material lets you make repairs that are a good match to the rest of the roof.

When you find your total square footage, divide by 100 to find the number of squares required. Round up to the nearest square. This is the total amount that you will need to cover your roof.

If the material you are pricing is shown with costs per square foot, take your total material amount and multiply by 100 to get the square footage needed. You can now multiply this times the cost per square foot of the material to get an accurate estimate of the roofing cost.

Common Metal Roof Sheet Sizes

Each type of metal roofing may come in a range of different sizes. Interlocking shingle panels, standing seam pans, flat sheets, corrugated sheets, and insulated panels may all come in a range of thicknesses and sizes.

If you are ordering your metal sheets directly from a manufacturer, you can have them cut to the exact length you need. For example, if your roof from edge to peak is 16′, you can have the sheets or pans cut to exactly 16′ so there is no seam in the center. For interlocking panels, tiles, and loose shingles, this type of sizing is not required.

Sheets typically come in widths of 26″ and 36″, while pans for standing seam roofs typically come in widths of 12″ to 18″. While sheets can be cut or trimmed to fit a roof evenly, you may want to choose a pan width for a standing seam roof that will give you a more even placement of seams across the roof for the best appearance.

Flat sheets, rolled roofing, and interlocking panels may all be trimmed to size as needed.

Metal roofs are beautiful and very durable. When installed correctly, they can last a very long time with little maintenance. See our other roofing resources for more roofing calculators and tools.

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Ice & Water Shield Calculator

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Ice & Water Shield Calculator

Enter the dimensions of the roof, eaves, and valleys to calculate the amount of ice and water barrier needed for a roof.

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How to Calculate Ice Barrier Needed

Ice barrier membrane, sometimes called ice and water shield, is a self-adhesive membrane installed for protecting roof underlayment. It adds an additional barrier against ice and water being forced into an asphalt shingle roof when ice dams form or during high winds and driving rain.

In cold climates, an ice barrier is often required by local codes. For example, states such as Minnesota require that an ice barrier membrane is installed extending 24″ beyond the inside of the exterior wall.[1]

Most localities that require an ice barrier stipulate that it cover from the edge of the eave to 24″ beyond the inside of the exterior wall.

To calculate the ice and water barrier needed for a roof, you need to measure the roof pitch, overhang of the eaves, and thickness of the exterior wall.

Ice Barrier Formula

Once you have the roof pitch, eave overhang, and wall thickness, you can use the following formula to calculate the coverage needed to protect 24″ beyond the exterior wall.

Most ice and water shield is sold in rolls that are 36″ in width and with varying lengths. The 36″ width ensures that it can cover the required or recommended amount on most roofs.

run = eave overhang + wall thickness + 24″
rise = run ÷ 12 × roof pitch
ice barrier coverage = run² + rise²

Once you calculate how far up the roof needs to be covered, you can calculate the total amount of ice and water barrier needed by multiplying the coverage in feet by the length of the eaves that need to be covered in feet.

total ice barrier required = ice barrier coverage × eave length

This will give you the amount of ice barrier square footage that is required. Because most rolls are sold in 36″ widths, if you know that you will need 36″ or less in width, you can simply measure the length of the area.

Typical roll lengths can range from 36′ to 75′. Simply find the total length that you need, and you can calculate how many rolls to purchase based on their size.

However, if you need more than 36″ in width for coverage, then finding the square footage required is a better method. You can find your width in inches if needed; take your length measurement in inches as well. Multiply them both together and divide by 144 to get the square footage.

Typical roll square footages are 108 sq. ft. to 225 sq. ft. If you are close to the total square footage for a roll, you may want to purchase an additional roll. This is because you will need to make several cuts in each roll to get the additional width needed, which means that you will have a greater than average amount of waste, and may need additional product to finish the job.

The calculator above applies all of these formulas to derive the amount of ice and water shield required for a roof.

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Window Air Conditioner Size Calculator

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Window Air Conditioner Size Calculator

Enter the length and width of your room to find the right sized window air conditioner to comfortably cool your space. Our calculator will recommend the number of BTUs needed to cool your room and will recommend an air conditioner that is the right size.

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How to Calculate the Window AC Unit Size You Need

There are many window air conditioner models and sizes available on the market to help cool your home, but choosing one can be quite confusing if you don’t know what size you need to cool your space.

Air conditioners are sized in a few different ways. Large air conditioners are sized by the ton, while smaller air conditioners may be sized by the number of square feet they are designed to cool or by the BTU.

BTUs stand for British Thermal Units and are the measure of energy required to raise the temperature of one pound of water by one degree Fahrenheit. Choosing the right size air conditioner for your room is very important.

If the air conditioner is too small, then the unit will run all day and will not be able to comfortably cool the room on warm days.

If the air conditioner is too big, then the unit will move too much air, causing it to cycle on and off too frequently. This may cause discomfort due to frequent blasts of cool air, then warm air. Frequent on/off cycles will also shorten the lifespan of the unit

In either case, an incorrectly sized unit will also use more energy. This will mean that your energy bills are higher than they could be with a correctly sized unit while you stay more comfortable at the same time.

Factors to Consider When Sizing an Air Conditioner

There are many factors to consider when sizing a window air conditioner. The main factor is the size of the room.

Room Size

The size of the room is the main factor in choosing a window air conditioner size. A larger room will naturally require more energy to cool and more airflow in CFM than a smaller room.

Window AC Size Chart

The chart below from Energy Star shows how many BTUs are needed for a given room size.[1]

Room Size (ft2) Capacity Needed (BTUs)
100 – 150 sq. ft. 5,000 BTUs
150 – 250 sq. ft. 6,000 BTUs
250 – 300 sq. ft. 7,000 BTUs
300 – 350 sq. ft. 8,000 BTUs
350 – 400 sq. ft. 9,000 BTUs
400 – 450 sq. ft. 10,000 BTUs
450 – 550 sq. ft. 12,000 BTUs
550 – 700 sq. ft. 14,000 BTUs
700 – 1,000 sq. ft. 18,000 BTUs
1,000 – 1,200 sq. ft. 21,000 BTUs
1,200 – 1,400 sq. ft. 23,000 BTUs
1,400 – 1,500 sq. ft. 24,000 BTUs
1,500 – 2,000 sq. ft. 30,000 BTUs
2,000 – 2,500 sq. ft. 34,00 BTUs

These air conditioner sizes assume a ceiling height of 8ft; if your ceiling is higher than 8ft, consider increasing the size in BTUs by 10% to account for the added volume of the room.

To find the size of the room you are planning on cooling, measure the length and width of the room in feet and multiply those two numbers together. Ideally, you want to be at the low to mid range of the unit’s capacity.

For example, to cool 1,100 sq ft, you would want a unit with 21,000 BTUs.

Sunlight

If the room gets a lot of sunlight, it will require additional energy to comfortably cool the room. Consider increasing the size of the air conditioner by 10% if the room gets a lot of sun.

To do this, take the size of the room in square feet, and add 10%, then find the recommended BTU range.

Kitchens and Cooking Appliances

Kitchens require much more energy to cool and require a larger air conditioner. Appliances add a lot of extra heat to a kitchen, making them tougher to cool. Consider the added heat of the oven or stove on a warm day.

When cooling a kitchen, consider adding an additional 4,000 BTUs to the size of the air conditioner.

Number of People

Body heat can warm a room significantly. The estimates above assume two occupants in the room. If your room has more than two people on a consistent basis, consider increasing the window air conditioner size by 10% – 20%.

Window Size

Window size can dictate how large of an air conditioner can be added to a room. If your room has windows that do not allow for the right size air conditioner, consider using two smaller units if your room has two windows, or consider an in-room air conditioner instead of a window unit.

Window units are available in different configurations as well as sizes. They should fit snugly, however; if the window is larger than the unit, you may need to add insulation or another material around the unit to help hold it in place and to stop thermal transfer around the unit

Electrical Power Available

Larger window air conditioners require more power. Some units require a dedicated circuit, while others require more current to the outlet. If the unit requires more power than you are able to provide, it may continually trip your circuit breaker. For example, if it needs its own circuit, but you plug in a vacuum on the same circuit, it will trip the breaker and stop both appliances from working.

Consider the amount and type of power available to the window and choose an air conditioner that will work with the existing wiring. If you can’t afford a dedicated circuit, take care not to use other appliances at the same time you use the air conditioner to avoid overloads.

If you’re unsure what your electrical requirements are, consider a consultation with an electrician.

Operating Cost

It’s important to also consider the operating cost of an air conditioner. Larger appliances consume more electricity and thus will cost more to operate. Use our electricity cost calculator to estimate how much it will cost to run the appliance.

Keep in mind that air conditioners are available with different energy efficiency levels. These are known as SEER levels or Seasonal Energy Efficiency Ratings. The higher the SEER, the less your unit will cost to run.

However, higher SEER units are also more costly. If you live in a climate where you need the air conditioner to run all day, it may be worthwhile to invest in a high SEER unit. However, if you only plan on using it periodically, a lower SEER unit may be your best choice.

If you’re sizing a heating system, check out our heating system BTU calculator.

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