Roofing Calculator
Converts horizontal footprint into sloped roof area using pitch as rise per 12 inches of run. Add waste for cuts and starter courses separately.
Step 1: Units
Step 2
Enter project measurements
Use decimals if needed (e.g. 3.5).
Step 3
How to use this calculator
Measure building outline for footprint length and width. Enter pitch like 6 for a 6:12 roof.
What the math is doing
Slope factor = sqrt(1 + (pitch/12)²). Roof area = footprint × slope factor.
Frequently asked questions
Hip roofs?
Break into planes or use a measured plan for accuracy.
Dormers?
Add each plane’s area.
Waste for shingles?
Often 10–15% on cut-up roofs; use waste field.
Flat roofs?
Pitch 0 gives footprint area only.