Free tool
Roofing Calculator
Enter the roof's footprint and pitch to estimate the roof area, the number of roofing squares and how many bundles of shingles to order.
How we calculate it
- Pitch multiplier = √(1 + (rise ÷ 12)²)
- Roof area = footprint length × width × pitch multiplier (or the area you enter)
- Squares = roof area ÷ 100, then × (1 + waste %)
- Bundles = squares with waste × the bundles per square on your wrapper, rounded up
The footprint method assumes one pitch over the whole roof. Ridge caps, starter strips, underlayment, flashing and tear-off are not included. This is an estimate, not a quote.
For roofers
How to use this tool
- Measure the roofEnter the footprint with overhangs and the pitch, or the roof area if you know it.
- Set the wasteChoose a waste allowance for cuts and the roof's shape.
- Enter your shinglesType the bundles per square from your shingle wrapper to get the bundle count.
Frequently asked questions
What is a roofing square?
A square is 100 square feet of roof surface. A roof with 2,000 square feet of surface is 20 squares. Shingles, underlayment and labor are often priced per square, so the calculator shows your roof in squares before and after the waste allowance you choose, ready to compare with a supplier's price.
How does roof pitch change the area?
A sloped roof has more surface than the ground it covers. Pitch is the rise in inches for every 12 inches of run, and the multiplier is the square root of 1 plus (rise divided by 12) squared. A 6/12 roof has about 11.8% more area than its footprint, so pitch matters.
How many bundles of shingles are in a square?
It varies by product, so this calculator does not assume a number. Your shingle wrapper or the manufacturer's spec sheet says how many bundles make a square, or how many square feet one bundle covers. If it gives square feet per bundle, divide 100 by that number and enter the result.
Is this a roofing quote?
No. It is a material estimate from the size and pitch you enter. Valleys, dormers, ridge caps, starter strips, flashing and tear-off are not included, and waste depends on the roof's shape. A roofer who measures the roof in person can give you an exact quantity and a price.