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This FAQ answers the most common questions about Smart Roofing Calculator. Topics include calculator accuracy (typically within 5-7% of professional takeoffs), why pitch matters for every estimate (it affects total surface area), how to choose the right waste factor for your roof type, what slope multiplier means, why our nail count assumes 4 nails per shingle (6 in high-wind zones), and how to combine multiple calculators for a full materials list. Use this page as your quick reference.
The questions that come up most often about measuring a roof, ordering material and pricing a job. Every figure below comes from the same functions the calculators on this site run.
| Pitch | Angle | Slope % | Multiplier | 2,000 sq ft footprint becomes |
|---|---|---|---|---|
| 1/12 | 4.8° | 8.3% | 1.0035 | 2,007 sq ft |
| 2/12 | 9.5° | 16.7% | 1.0138 | 2,028 sq ft |
| 3/12 | 14.0° | 25.0% | 1.0308 | 2,062 sq ft |
| 4/12 | 18.4° | 33.3% | 1.0541 | 2,108 sq ft |
| 5/12 | 22.6° | 41.7% | 1.0833 | 2,167 sq ft |
| 6/12 | 26.6° | 50.0% | 1.1180 | 2,236 sq ft |
| 7/12 | 30.3° | 58.3% | 1.1577 | 2,315 sq ft |
| 8/12 | 33.7° | 66.7% | 1.2019 | 2,404 sq ft |
| 9/12 | 36.9° | 75.0% | 1.2500 | 2,500 sq ft |
| 10/12 | 39.8° | 83.3% | 1.3017 | 2,603 sq ft |
| 12/12 | 45.0° | 100.0% | 1.4142 | 2,828 sq ft |
| 14/12 | 49.4° | 116.7% | 1.5366 | 3,073 sq ft |
| 16/12 | 53.1° | 133.3% | 1.6667 | 3,333 sq ft |
| 18/12 | 56.3° | 150.0% | 1.8028 | 3,606 sq ft |
| 20/12 | 59.0° | 166.7% | 1.9437 | 3,887 sq ft |
| 24/12 | 63.4° | 200.0% | 2.2361 | 4,472 sq ft |
Measure the building footprint to the outside of the eaves and rakes, then multiply by the pitch factor. A 2,000 square foot footprint at 6/12 pitch is 2,236 square feet of roof.
Three bundles per square for most architectural and three-tab shingles. Work out your squares first — roof area divided by 100 — then add 10% to 20% waste depending on how cut-up the roof is.
One hundred square feet of finished roof surface. Roofing material is priced and ordered by the square.
No. Nothing on this site requires a sign-in, an email address or a trial, and every calculation runs in your browser rather than on a server.