Roof Square Footage Calculator
Measure the footprint of the roof including the overhangs, then pick the pitch (inches of rise per 12 inches of run).
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Most shingle bundles cover 33.3 sq ft, so three bundles make one square (100 sq ft).
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Roof squares and pitch
Roofers measure in squares: one square covers 100 square feet. Most shingles come three bundles to a square.
A steeper roof has more surface than its footprint. The pitch factor converts the flat area to the real roof area: a 6/12 pitch adds about 12%, a 12/12 pitch about 41%. Add around 10% for waste on simple roofs and 15% or more for roofs with valleys, hips and dormers.
Roof pitch multipliers
| Pitch | Angle | Multiplier | 1,500 sq ft footprint |
|---|---|---|---|
| 2/12 | 9.5° | 1.014 | 1,521 sq ft |
| 3/12 | 14° | 1.031 | 1,546 sq ft |
| 4/12 | 18.4° | 1.054 | 1,581 sq ft |
| 5/12 | 22.6° | 1.083 | 1,625 sq ft |
| 6/12 | 26.6° | 1.118 | 1,677 sq ft |
| 7/12 | 30.3° | 1.158 | 1,737 sq ft |
| 8/12 | 33.7° | 1.202 | 1,803 sq ft |
| 9/12 | 36.9° | 1.25 | 1,875 sq ft |
| 10/12 | 39.8° | 1.302 | 1,953 sq ft |
| 11/12 | 42.5° | 1.357 | 2,035 sq ft |
| 12/12 | 45° | 1.414 | 2,121 sq ft |
Roof area = footprint area × √(1 + (pitch ÷ 12)²)
Questions
What is a roofing square?
100 square feet of roof surface.
How much waste should I add for shingles?
About 10% for a simple gable roof and 15% or more for hips, valleys and dormers.