How Many Shingles Do I Need? (Roofing Calculation Guide)

By Amanda Lutz Updated February 6, 2024

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Shingles are one of the most popular roofing materials in the country. To determine the total cost of a shingle roof replacement, you’ll first need to estimate how many shingles you need. We’ll explain how to measure and calculate your roof’s surface area and pitch to figure out how many shingle bundles you need to buy for your project.

 

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How to Calculate the Area of Your Roof

Your roof’s square footage will be larger than your home’s square footage to account for overhangs, dormers, and other features. For this calculation, measure the height and width of each plane—that is, each flat surface on the roof that’s covered in shingles. We recommend first making a simple diagram of your roof. As you measure, fill in the roof dimensions on the appropriate part of the diagram to ensure you don’t miss any spots.

Practice good ladder and roof safety as you measure. For height measurements, stand at the roof peak and advance your tape measure down to the roof edge. For width measurements, measure along the eaves from one edge or ridge to another. You’ll also want to measure any nonshingled surfaces such as chimneys or vents; you’ll subtract these out of the final measurements. The simplest roofs, gable roofs, have only two rectangular planes, but hip roofs and other styles may have triangular or trapezoidal planes.

Here are the measurements you’ll need for each plane shape and how to calculate each surface area.

• Rectangle or square: Measure your roof’s height and length, and multiply those measurements. (e.g. 10-foot height and 15-foot length = 10 feet x 15 feet = 150 square feet)
• Trapezoid: Measure the top length of the plane, bottom edges, and height. Add the length measurements, multiply by height, and divide by two. (e.g. 8-foot top length, 12-foot bottom length, and 6-foot height = [(8 feet + 12 feet) x 6 feet]/2 = [20 feet x 6 feet]/2 = 60 square feet)
• Triangle: Measure the base and height from the base to the triangle’s peak, then multiply the base times the height and divide by two. (e.g.12-foot base and 10-foot height = (12 feet x 10 feet)/2 = 60 square feet)

Once you have the square footage of the individual planes, including dormers, add them to get the total surface area of the roof. Subtract the area of nonshingled surfaces to find the square footage of the roof that needs to be covered in shingles. Keep in mind, some roofing companies may measure by roofing square not square feet so be sure to check which measurement is being used.

 

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How to Calculate the Pitch of Your Roof

Roof pitch, also called roof slope, determines how much the shingles should overlap. Steep roofs will require slightly more shingles, so calculating pitch will give you a multiplier to adjust your square footage. You won’t need the same multiplier to buy underlayment or other roofing materials. Note that pitch is expressed as a ratio of vertical rise to horizontal run, so a pitch of 6:12 indicates that a roof rises six inches in height for every 12 inches of roof length.

To measure your roof’s pitch, use a level that’s at least 12 inches long and a tape measure. Follow these instructions to find your roof’s pitch.

1. On your roof, rest one end of the level against the shingles and adjust the other end until the level is perfectly horizontal.
2. Use your tape measure to measure the distance from the roof’s surface to the 12-inch mark on the level. Round this to the nearest whole number; it will serve as the rise, and the run is 12.
3. Find the appropriate multiplier on the table below and use it to adjust the total roof area for pitch.

Roof Slope	Multiplier
3:12	1.031
4:12	1.054
5:12	1.083
6:12	1.118
7:12	1.158
8:12	1.202
9:12	1.25

For example, if your roof is 2,186 square feet and has a pitch of 5:12, you would multiply 2,186 by 1.083 to get an adjusted total of 2,368 square feet. Shingles and other materials are sometimes measured by the roofing square, which is an area of 100 square feet. You can divide the total by 100 to get the number of roofing squares you need to cover; 2,368 square feet is equivalent to 23.68 squares of shingles.

 

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How to Choose the Type of Shingles for Your Roof

Shingles are a good choice for nearly all roof sizes and shapes aside from flat roofs. Although asphalt shingles are the most common, you can choose from many materials at different price points.

• Asphalt: Three-tab shingles are the most cost-effective asphalt option, but you can find architectural asphalt shingles that are a bit more durable for a higher price. These shingles last about 30 years.
• Composite: Composite shingles combine asphalt with plastic, fiberglass, and other materials. These are more durable than other shingles, particularly in severe weather. However, they tend to cost about twice as much as asphalt shingles.
• Metal: There are several types of metal roofing, but metal shingles are typically made of steel, copper, or zinc. Steel is durable and moderately priced, whereas copper and zinc are expensive but can last a century or more when properly installed.
• Slate: Slate shingles are thin tiles of natural stone, which means they’re extremely strong but also very heavy. They usually require extra roof reinforcement, and while they can last more than 100 years, they’re often the most expensive type of shingle.
• Wood: Wooden shakes and shingles are typically made of cedar or redwood. They’re not overly expensive, but they require a lot of maintenance. They need to be regularly inspected and sealed, and they’re not fire-resistant.

 

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How to Estimate the Number of Shingles You Need

Once you’ve chosen the type of shingle you want, you can use your pitch-adjusted square footage to calculate the number of bundles to buy. All types of shingles come in bundles that cover approximately 33 square feet of roof. That’s three bundles for every roofing square. Take the number of squares you calculated above—in our example, 23.68—and round that number, then multiply by three to get 72 shingle bundles.

When making your calculations, plan for some overage in case of wasted shingles. Some shingles will need to be cut to shape or used as valley or ridge caps, and a few shingles may arrive cracked or unusable. Plan for about 15% wastage, so multiply the number of bundles by 1.15 to get the final number of shingles you need. In our example, 72 x 1.15 = 82.8 rounded to 83. To cover a roof of 2,186 square feet and a pitch of 5:12, you’ll need a total of 83 shingle bundles. Use an online shingle calculator to help with this math if you get stuck.

 

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How to Hire a Professional

You can measure your roof and calculate the amount of material yourself, but your actual roofing project should be completed by a licensed professional. A pro can also assist with measuring and calculating the roofing materials you need. Here’s what to look for when hiring a roofing contractor.

• Roofers must be licensed with the state to offer their services. Ask the company for proof of current licensure.
• Ask for proof that all contractors working on your home are bonded and insured. This prevents you from being held responsible in case of injuries or damage.
• Search the Better Business Bureau (BBB) website for information on the roofing company, including ownership information, rating, accreditation status, and any customer complaints.
• Ask for references from satisfied customers, and check reputable customer review sites such as Trustpilot.
• Ask about warranties or guarantees on workmanship.
• Get quotes from at least three local contractors to get a better sense of the price range in your area.

 

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Our Recommendation

Roofing a house is a substantial financial investment. To estimate your total price, you’ll need to calculate how many shingles you need to cover your roof. Use the steps and formulas provided above to find your roof’s square footage and pitch to estimate the number of bundles you’ll need to buy. A professional roofing contractor can also assist you with these calculations.

 

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