Guide / Roof measurement, United States

How many squares is my roof?

Toshikatsu Oga / September 27, 2026

What a square is
The pitch factor
The footprint
Waste, hips and valleys
Using the count to check the shingle line
What to do
Questions
Sources

A roofing square is 100 square feet of roof surface. To estimate your own count, multiply the footprint of the house, including overhangs, by the pitch factor for the slope and divide by 100. The factor is the square root of 1 plus (rise over 12) squared: 1.054 for 4/12, 1.118 for 6/12, 1.202 for 8/12, 1.302 for 10/12 and 1.414 for 12/12. A 2,000 square foot footprint at 6/12 is 2,236 square feet, or about 22.4 squares before waste. The count matters because the shingle line, the tear-off line and the labor line on a quote all scale with it, and because the public floor for shingles, about $82 to $89 per square in the current data (Census IMDB 2026-07, Census AIES 2024), is only useful if you know how many squares you are multiplying.

What a square is

Roofers price and buy shingles by the square, which is 100 square feet of finished roof surface, not of floor area. Three bundles of standard architectural shingles usually make a square, and the product sheet will say so. A 26 square roof is 2,600 square feet of surface, on a house whose footprint is smaller than that, because the roof is tilted and overhangs the walls.

The pitch factor

Roof slope is written as rise over run: a 6/12 roof rises six inches for every twelve inches it runs. The slanted surface is longer than the flat footprint by a factor of the square root of (1 + (rise/12) squared). That is plain geometry, and you can check it on a calculator.

Pitch	Rise per 12 in. of run	Factor	2,000 sq ft footprint
3/12	3 in.	1.031	2,062 sq ft, 20.6 squares
4/12	4 in.	1.054	2,108 sq ft, 21.1 squares
5/12	5 in.	1.083	2,167 sq ft, 21.7 squares
6/12	6 in.	1.118	2,236 sq ft, 22.4 squares
8/12	8 in.	1.202	2,404 sq ft, 24.0 squares
10/12	10 in.	1.302	2,603 sq ft, 26.0 squares
12/12	12 in.	1.414	2,828 sq ft, 28.3 squares

You can read the pitch off a level and a tape in the attic, or from the plans. It is worth the trip: the difference between 4/12 and 8/12 is about 14% of the count, and the count drives the shingle line, the tear-off line and the labor line.

The footprint

Measure the outside of the house along the ground, wall by wall, and add the eave overhang on each side, typically one to two feet. A rectangular house 50 by 40 feet with 18 inch overhangs is 53 by 43 feet, or 2,279 square feet of footprint. Attached garages, porches and bay windows under the same roof count; a detached shed does not. The county appraisal district record usually gives a building footprint you can start from, but it will not include overhangs.

Waste, hips and valleys

Quotes include a waste allowance on top of the measured squares, because shingles are cut at hips, valleys, ridges and edges. The percentage is the contractor's choice and depends on the roof: a plain gable roof needs less than a roof with several hips and valleys. The number to ask for is the percentage, so that you can separate the measured squares from the allowance. If a quote says 30 squares and your calculation says 24, a 10% or 15% allowance explains 26 or 28; the rest is a question.

Using the count to check the shingle line

Once you trust the count, the shingle line can be tested against public data. The Census import record for asphalt roofing gives a landed duty-paid value of $0.4667 per kilogram for January to July 2026 (Census IMDB 2026-07); the wholesale gross margin for roofing distributors is 28.35% (Census AIES 2024); state DOT rules allow a contractor materials markup of 15% to 25% (Caltrans, FDOT, TxDOT). At 240 pounds per square, which is 108.86 kilograms, that chain gives about $82 to $89 per square, so 26 squares are $2,120 to $2,304 as a floor. Freight to your street, brand and any extra distributor tier sit on top. The full arithmetic is in what a roof replacement should cost in Austin.

The count also checks two other lines. The tear-off should be priced on the same squares as the shingles, and the labor hours should make sense for the count: a three-person crew stripping and laying 26 squares in three days is ordinary; the same crew taking three days for 12 squares is a question.

What to do

Compute your own count from the footprint and the pitch factor.
Ask the contractor for the measured squares and the waste percentage separately.
Check that the tear-off and the shingles use the same number.
Multiply the squares by $82 and by $89 (Census IMDB, Census AIES) and see how far above the floor the shingle line sits; then ask what brand, freight and tier explain the gap.

Our Quote Check does the count from your footprint and pitch when the quote does not state squares, and prints the factor it used. Every number in the report carries its source and formula. We are paid by homeowners only and take no fee from contractors. Check a quote from $39, or run the free Quick Estimate first.

Questions

How many square feet is a roofing square?

100 square feet of roof surface. A 26 square roof is 2,600 square feet of surface.

How do I calculate the squares on my roof?

Multiply the footprint of the house including overhangs by the pitch factor for the slope, then divide by 100. The factor is 1.054 for 4/12, 1.118 for 6/12, 1.202 for 8/12, 1.302 for 10/12 and 1.414 for 12/12.

How much waste should a roofing quote include?

The contractor decides, and it depends on hips, valleys and the shape of the roof. Ask for the measured squares and the waste percentage as separate numbers so you can see both.

What is the public floor for a square of asphalt shingles?

About $82 to $89 per square at 240 pounds per square in the current data, from the Census import value of $0.4667 per kilogram, the wholesale gross margin of 28.35% and a contractor markup of 15% to 25%. Freight, brand and extra distribution tiers add to it.

Sources

Every figure above links to the public record it comes from. The wage, import, margin and markup figures are the ones our reports use, published as USCCDB v1.0 under CC BY 4.0. Statutes and city pages are quoted as published on September 27, 2026; check the source for changes.

How we work: HORIZON SHIELD is paid by homeowners only. We take no referral fee, listing fee or commission from any contractor, distributor or insurer, so the only way we earn is by finding what is in the quote. Every report prints the source and the formula beside every number, and a sha256 receipt so the contractor can confirm the report was not altered. About the service.