Roofing Calculator
Measure the house footprint, including the overhangs, and pick the pitch. You get the real roof surface, the number of squares, and the shingle bundles to order.
- Shingle bundles (3 per square)
- 56
- Pitch multiplier
- 1.118
- Roof angle
- 26.6°
Pitch multipliers
A sloped roof has more surface than the footprint under it. Multiply the footprint by the pitch factor, which is √(1 + (rise ÷ 12)²).
| Pitch | Angle | Multiplier |
|---|---|---|
| 3/12 | 14.0° | 1.031 |
| 4/12 | 18.4° | 1.054 |
| 5/12 | 22.6° | 1.083 |
| 6/12 | 26.6° | 1.118 |
| 7/12 | 30.3° | 1.158 |
| 8/12 | 33.7° | 1.202 |
| 9/12 | 36.9° | 1.250 |
| 10/12 | 39.8° | 1.302 |
| 12/12 | 45.0° | 1.414 |
Squares and bundles
A roofing square is 100 sq ft. Most 3-tab and architectural shingles come three bundles to the square. Some heavy designer shingles take four or five, so check the wrapper. Starter strip and ridge cap are sold separately and are not included here.
Example: a 50 × 30 ft footprint at 6/12 has 1,677 sq ft of roof. With 10 % waste that is 18.4 squares, or 56 bundles.
The multiplier works for any roof whose planes all share one pitch, including hip roofs. Dormers and mixed pitches should be measured plane by plane.