Roofing Calculator — How Many Shingles Do I Need?
Enter your roof footprint and pitch to get shingle bundles, roofing squares, and underlayment rolls needed.
How to Calculate Roofing Materials
Start with your roof's footprint (the house dimensions from above, not the actual sloped surface). Multiply length × width to get the footprint area, then multiply by a pitch factor to get the true roof surface area — a steeper roof has more actual surface than its footprint suggests.
Divide the roof area by 100 to get roofing squares (the standard unit roofers use), then multiply by bundles-per-square for your shingle type. Always add a waste factor for cuts at ridges, valleys, and edges.
Roof Pitch Multipliers
| Pitch | Multiplier | Extra Area vs. Footprint |
|---|---|---|
| 3:12 | 1.031 | +3% |
| 5:12 | 1.083 | +8% |
| 6:12 | 1.118 | +12% |
| 8:12 | 1.202 | +20% |
| 10:12 | 1.302 | +30% |
| 12:12 | 1.414 | +41% |
A 2,000 sq ft footprint at a 6:12 pitch has roughly 2,236 sq ft of actual roof surface — that's the number your shingle order needs to be based on, not the footprint.
Frequently Asked Questions
How many bundles of shingles do I need per square?
Most standard 3-tab and architectural asphalt shingles come 3 bundles per square (100 sq ft). Heavier wood shake typically needs 4 bundles per square.
How does roof pitch affect the amount of shingles I need?
A steeper pitch means more actual roof surface area than the home's footprint suggests. A 6:12 pitch adds about 12% more area than the flat footprint; a 12:12 pitch adds about 41%.
What is a roofing square?
A roofing square equals 100 square feet of roof surface. It's the standard unit roofers and suppliers use to price and order materials.
How much waste should I add for a roofing job?
Add 10% for a simple gable roof, and 15% for roofs with hips, valleys, or dormers, since those features create more angled cuts and offcuts.