Roof Pitch Calculator
Calculates roof pitch, angle and rafter length from rise and run.
Enter Values
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Enter the roof's rise and run.
- Press Calculate for the angle and the pitch ratio.
How it works
Roof pitch is the steepness of a roof. From the rise and run, the angle is arctan(rise ÷ run), and the ratio is expressed as rise per 12 of run (for example 6:12).
Worked example
Rise 1, run 1. Angle = 45°, ratio 12:12.
Common mistakes
- Mixing pitch as a ratio with pitch in degrees — 1:1 is 45°, not 1°.
- Measuring rise and run over different spans; use the same horizontal run for both.
Frequently asked questions
How is roof pitch calculated?
Pitch is rise over run. As an angle it is arctan(rise ÷ run); as a ratio it is written like 1:2, or as x-in-12 in imperial.
What is a common roof pitch?
Many houses sit between about 15° and 30° (roughly 4-in-12 to 7-in-12); low-slope roofs under about 10° need different materials.
What's a common roof pitch?
Many homes sit between 4:12 and 9:12.
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Cite this tool
Zerdly. (2026). Roof Pitch Calculator. Retrieved from https://www.zerdly.com/tools/roof-pitch-calculator/
Tip: Enter any known values to calculate the remaining results.
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