Roof Pitch Calculator
By Miikka · CalcBrew · Updated
20.6 °
Pitch
| Pitch in degrees | 20.6 ° |
| Pitch in percent | 37.5 % |
| Ratio (rise/run) | 0.375 |
The roof pitch calculator converts a roof's slope into degrees and percent and shows it as a ratio. Enter the rise and the horizontal run, and you get all three ways of expressing the pitch at once.
How the calculator works and what it’s for▾
How the pitch is calculated
Pitch in percent is found by dividing the rise by the horizontal run and multiplying by one hundred. Pitch in degrees comes from arctan(rise/run), which turns the ratio into an angle.
The ratio expresses the relationship between rise and run directly, for example in the form 1:3.
What you enter and what you get
You enter the rise, the vertical height, and the horizontal run, the horizontal distance, both in millimetres.
The result shows the pitch in degrees, in percent and as a ratio, so you can compare it against the requirements of your roofing material manufacturer.
Who finds it useful
The calculator suits planning a re-roof or a new build when you need to confirm that the roof pitch fits the chosen covering.
Different roofing materials have their own minimum pitches, so knowing the slope helps you pick a workable, watertight solution.
Measuring tips
Measure the rise and run at the same point on the roof and use the same unit for both, so the ratio stays correct. On low-slope roofs even small measuring errors affect the result.
Always check the roofing manufacturer's guidance on minimum pitch before making the final decision.
🔄 Reviewed June 2026
Frequently asked questions
Cite this calculator
CalcBrew. (2026). Roof Pitch Calculator. https://calcbrew.com/roof-pitch-calculator“Roof Pitch Calculator.” CalcBrew, 2026, calcbrew.com/roof-pitch-calculator.Link to https://calcbrew.com/roof-pitch-calculator. Results are estimates; cite the underlying formula or data source for academic work.
Related tools
More in Home & Construction · All calculators