Roofing calculator
Roof area, squares and bundles of shingles from the footprint and the pitch.
A 40 × 30 ft footprint under a 6/12 roof is 1,342 ft² of roof: 13.42 squares, 45 bundles of shingles with 10 % extra.
Measure
Roof
1,342 ft² · pitch factor 1.118
Your shopping list
Shingles
45 bundles
14.76 squares with 10 % extra
A roofer's quote
14.76 squares
A square is 100 ft² (9.29 m²) of roof
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How it is calculated
- Footprint40 ft × 30 ft = 1,200 ft²
- Pitch factor√(1 + (6 ÷ 12)²) = 1.118
- Roof area1,200 × 1.118 = 1,342 ft², 13.42 squares
- Bundles13.42 × 1.10 × 3 = 45 bundles
Pitch factor and angle
| Pitch | Angle | Pitch factor |
|---|---|---|
| 2/12 | 9.5° | 1.014 |
| 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 by house footprint
Footprint with the overhang. Bundles at 6/12 with 10 % extra.
| Footprint | 4/12 | 6/12 | 8/12 | Bundles at 6/12 |
|---|---|---|---|---|
| 1,000 ft² | 10.54 | 11.18 | 12.02 | 37 |
| 1,500 ft² | 15.81 | 16.77 | 18.03 | 56 |
| 2,000 ft² | 21.08 | 22.36 | 24.04 | 74 |
| 2,500 ft² | 26.35 | 27.95 | 30.05 | 93 |
| 3,000 ft² | 31.62 | 33.54 | 36.06 | 111 |
Frequently asked questions
How many bundles of shingles are in a square?
3 bundles cover one square (100 ft²) of architectural shingles such as GAF Timberline HDZ, 64 pieces per square. If the wrapper of your brand says otherwise, change "Bundles per square".
How do I calculate roofing squares?
Measure the footprint with the overhang, multiply by the pitch factor, then divide by 100. A 40 × 30 ft footprint at 6/12: 1,200 × 1.118 = 1,342 ft², so 13.42 squares.
What is the pitch factor of a 6/12 roof?
1.118: the square root of 1 + (6 ÷ 12)². A 6/12 roof rises 6 inches per foot and slopes 26.6°. At 12/12 the factor is 1.414 (45°).
How many squares is a 2,000 sq ft roof footprint?
At 6/12, 22.36 squares of roof, and 74 bundles of 3-bundle shingles with 10 % extra. At 8/12, 24.04 squares.
How much extra shingle should I buy?
The calculator adds 10 % for cuts, starter and ridge courses on a simple gable roof. Raise it for hips, valleys and dormers, where more shingles are cut.