What is a roofing square?
A roofing square is 100 square feet of roof surface. Here is how to calculate squares for any roof — and why the pitch matters.
Roofers don’t price roofs in square feet. They use squares, and one square equals 100 square feet of roof surface. A 2,500 sq ft roof is 25 squares; a 3,200 sq ft roof is 32 squares.
Why roofers use squares
Shingles are packaged by the square. Most standard asphalt shingles come three bundles to a square, so “25 squares” immediately tells a roofer how much material to order and roughly how much labor the job takes.
Roof area is not the same as house size
The number that matters is the sloped surface of the roof, which is always larger than the floor area of the house, for two reasons:
- Overhangs. The roof extends past the walls, usually 12–24 inches on every side.
- Pitch. A sloped roof has more surface than the flat footprint under it. A 6/12 roof has about 12% more surface; a 12/12 roof about 41% more.
How to calculate roofing squares
- Measure the footprint including overhangs (length × width for a simple rectangle).
- Multiply by the pitch multiplier for your roof’s slope.
- Divide by 100.
- Add waste — typically 10–15% — and round up.
Squares, bundles and waste at a glance
| Roof area | Squares | +12% waste | Bundles (3/sq) |
|---|---|---|---|
| 1,500 sq ft | 15 | 16.8 | 51 |
| 2,000 sq ft | 20 | 22.4 | 68 |
| 2,500 sq ft | 25 | 28.0 | 85 |
| 3,000 sq ft | 30 | 33.6 | 101 |
| 3,500 sq ft | 35 | 39.2 | 118 |
| 4,000 sq ft | 40 | 44.8 | 135 |
For a quick estimate use the free roof squares calculator. For an actual measurement of an L-shaped or hip roof, a Horus report measures every plane from aerial imagery.