Roof Pitch Calculator
Calculate roof pitch as rise over 12, slope ratio, angle in degrees, percent grade, and rafter length from rise and run.
Formula
Pitch x:12 = (rise ÷ run) × 12. Angle = arctan(rise ÷ run). Rafter length = √(rise² + run²).
Assumptions
- Rise and run describe a single roof plane in consistent units.
Limitations
- Geometric estimates only — roof design and structural suitability require qualified professionals.
- Field measurements and local building codes must be verified.
Worked example
Rise 4 ft, run 12 ft
Pitch = 4:12. Angle ≈ 18.43°. Rafter length for one run = √(4² + 12²) ≈ 12.65 ft.
Frequently asked questions
What does 4:12 pitch mean?
A 4:12 pitch rises 4 inches for every 12 inches of horizontal run. The calculator normalizes any rise and run to this standard format.
Last reviewed: 2026-07-23
Category: Construction & Materials
Results are provided for informational purposes only and may not reflect real-world policies, fees, or individual circumstances.