Roofing Calculator
Estimate your roof area and shingle needs. Enter the footprint the roof covers and its pitch to get the area in roofing squares and the number of shingle bundles.
Roofers measure in "squares" — each one is 100 square feet of roof surface. The tricky part is that a roof's surface is larger than the footprint it covers, because it slopes. Multiplying the footprint by a pitch factor gives the true surface area, which you then convert to squares and shingle bundles. This calculator handles the pitch adjustment and waste so you can estimate materials without climbing up to measure every plane.
How to estimate roofing
Take the ground area the roof covers, multiply by a factor for the pitch to get the sloped surface area, divide by 100 for squares, and figure three bundles per square.
Squares = Roof area ÷ 100
Bundles ≈ Squares × 3 (× 1 + waste)
| Pitch | Factor |
|---|---|
| 4 / 12 | 1.054 |
| 6 / 12 | 1.118 |
| 8 / 12 | 1.202 |
| 12 / 12 | 1.414 |
Worked example
A 50 ft × 30 ft footprint with a 6/12 pitch and 10% waste:
| Footprint = 50 × 30 | 1,500 sq ft |
| Roof area = 1,500 × 1.118 | 1,677 sq ft |
| Squares (16.8) × 3 bundles + 10% | ≈ 56 bundles |
What the estimate leaves out
This gives the field area — the main shingled surface. On top of that you'll need starter shingles along the eaves and rakes, hip and ridge caps along the peaks, plus underlayment, drip edge, flashing and nails. Complex roofs with many valleys, dormers and penetrations waste more material, so lean toward the higher end of the waste range for them. For a firm quote and to confirm structural details, measure each roof plane directly or have a roofer assess it.