About the Roof Pitch Calculator
Roof pitch can be written four ways: an angle, a rise-over-run ratio such as 6:12, a percentage, or simply the rise for a known span. They all describe the same slope. Enter whichever one you have and this calculator gives the rest, along with the rafter length multiplier you need for ordering timber.
Also known as: roof angle calculator, roof slope calculator, pitch to degrees, 6/12 pitch, roof rise and run.
How to use this calculator
- Enter i know the and the other fields.
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
pitch angle = arctan(rise ÷ run) · multiplier = √(1 + (rise/run)²)
Worked example
Using the values pre-filled in the calculator above:
- I know the: Rise and run
- Rise = 2 m
- Run (half the span) = 4 m
the calculator returns:
- Pitch angle: 26.565 °
- Ratio: 6 : 12
- Percentage: 50 %
- Rise per metre of run: 0.5 m