Calculators
Roof area and squares calculator
Safety verdict: Safe from the ground measured from the ground, the attic, or a scaled photograph
Footprint, not roof surface
Include the overhang
6 means 6:12
10% simple roof, 15%+ with valleys
- Footprint area
- —
- Pitch multiplier
- —
- Roof surface
- —
- Squares (with waste)
- —
- Bundles (3 per square)
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Turn a building footprint and a pitch into actual roof area, roofing squares and bundle count — with the pitch multiplier shown, not hidden.
The formula
roof area = footprint x sqrt(rise^2 + 12^2) / 12 ; squares = roof area / 100
Assumptions
- A roofing square is 100 square feet. Every bid you receive will be priced in squares.
- Three bundles of standard architectural shingle cover one square. Luxury and some designer lines run four or five.
- The waste factor covers starter course, ridge cap and cut-off at valleys and hips. A simple gable roof needs about 10%; a roof with several valleys, dormers or a complex hip needs 15% or more.
- This estimates the roof plane only. It does not price the job, and it does not account for tear-off of existing layers.
Reference table
| Pitch | Multiplier | 1,200 sq ft | 2,000 sq ft |
|---|---|---|---|
| 2:12 | 1.014 | 12.2 | 20.3 |
| 4:12 | 1.054 | 12.6 | 21.1 |
| 6:12 | 1.118 | 13.4 | 22.4 |
| 8:12 | 1.202 | 14.4 | 24.0 |
| 10:12 | 1.302 | 15.6 | 26.0 |
| 12:12 | 1.414 | 17.0 | 28.3 |