Shingle Calculator

How to calculate how many shingles you need

Shingles are sold in bundles, and roofers count them by the roofing square, which is 100 square feet of roof. Start with the real area of every plane of the roof, not the floor plan under it. If you only know the size of the house, the roofing calculator turns a footprint and a pitch into roof area.

A rectangular plane is length times width. The triangular plane at the end of a hip roof is base times height divided by 2. Each plane is its own row, so a gable roof is two rows and a hip roof is two rectangles and two triangles. Measurements can be typed as 14'6" or 14 ft 6 in, and the calculator rounds every bundle count up because you cannot buy part of a bundle.

Example: a gable roof with two planes

Each plane is 40 ft by 14.5 ft measured on the slope. You use shingles that come 3 bundles per square, add 10% waste, and your eaves and rakes add up to 138 ft (80 ft of eaves plus four rakes of 14.5 ft). The ridge is 40 ft. The starter is GAF Pro-Start and the caps are GAF Seal-A-Ridge.

Bundles for a given number of squares

The table shows the bundles for a roof area with no waste added. Waste goes on top of these numbers.

Bundles per square and coverage per bundle

This Old House says shingles come in bundles that cover about 33 square feet, so three bundles make a square. Fine Homebuilding adds that three bundles to the square is the most common, which applies to most 3-tab and some lightweight laminated shingles, while heavier shingles take four or sometimes five. Both were checked in October 2026. The exact coverage of a product is printed on its package, and the “Custom coverage” option lets you use it.

Starter strip and ridge cap bundles

Starter strip goes along the eaves and rakes, and ridge caps go along the ridge and the hips. Each is a separate product with its own coverage per bundle. These are the figures we read in the manufacturers’ data sheets and in a trade magazine in October 2026:

GAF states that four bundles of Seal-A-Ridge cover approximately 100 linear feet, so the table shows 100 ÷ 4 = 25 feet per bundle. The GAF and Owens Corning sheets are the manufacturers’ own documents, read from copies hosted by retailers and distributors because the manufacturers’ websites do not serve them to automatic readers. The Owens Corning starter sheet says it works with shingles that have an exposure of up to 6 inches. For valleys, Fine Homebuilding recommends two extra shingles per linear foot, and its example is a 16 ft valley that needs 32 shingles, roughly one extra bundle. The calculator shows that count but does not add it to the bundles.

How much waste to add

Leave the waste box empty to see the exact amount. The published advice differs:

• This Old House says to include an extra 15% for waste from cuts around vents, pipes and ridge caps.
• GAF suggests adding 10-15% for trim allowance and waste.
• Fine Homebuilding author Mike Guertin figures 1% on a simple roof and 5% or more on a complex roof, and he works out starter shingles and caps separately, which is why this calculator does too.

A roof with many hips, valleys and dormers wastes more than a plain gable. Ask your supplier or roofer which percentage they use. Figures checked in October 2026.

What this calculator does not do

It counts asphalt shingle bundles from the areas and lengths you type. It does not give prices, and it does not count nails, underlayment, flashing, drip edge or vents. It does not cover wood shingles either, because we could not verify their coverage. To find the roof area from the size of the house, use the roofing calculator, and to turn a pitch into degrees or a rise, use the roof pitch calculator.

Frequently asked questions