🏠 Roofing Calculator
Enter the length and width of the area the roof covers (including overhangs) and the roof pitch.
How the Roofing Calculator works
The footprint is multiplied by a pitch factor to get the sloped roof area. One roofing square is 100 ft², and standard architectural shingles usually come 3 bundles per square.
Step-by-step calculation
- 1Measure the footprint including overhangs.
- 2Multiply by the pitch factor.
- 3Add waste and divide by 100 for squares.
- 4Multiply squares by 3 for bundles.
Worked example
A 40 × 30 ft footprint with a 6/12 pitch: 1,200 × 1.118 = 1,342 ft². With 10% waste that is 14.8 squares, or 45 bundles.
Roofing Calculator examples
| Footprint length incl. overhang (ft) | Roofing needed |
|---|---|
| 20 | 7.4 squares |
| 30 | 11.1 squares |
| 40 | 14.8 squares |
| 50 | 18.4 squares |
| 60 | 22.1 squares |
Other inputs kept at the calculator's default values. Results calculated by this calculator.
Why use a Roofing Calculator?
Estimate shingles for a roof replacement.
Important factors that can affect your results
- Valleys, hips and dormers.
- Ridge caps and starter strips.
- Local code requirements.
Frequently asked questions
How do I find the pitch?
Measure how many inches the roof rises over 12 inches of horizontal run.
Does this include ridge caps and starter strips?
Not separately — the waste allowance covers some of it; ask your supplier for exact accessories.
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Last reviewed November 2026 · How we build and check our tools · Report a problem