Roof pitch calculator
Enter the vertical rise and horizontal run in the same unit, such as 6 inches per 12 or 30 cm per 100 cm.
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How to use it
- Enter rise and run.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
Angle = arctan(rise ÷ run). Percent = rise ÷ run × 100. Pitch in 12 = 12 × rise ÷ run. Rafter factor = √(1 + (rise ÷ run)²).
Example
Inputs: Rise = 6, Run = 12. Result: Pitch angle: 26.57 °; Pitch in 12: 6 in 12; Slope percent: 50%.
Limits and caveats
- Assumes a flat plane with a constant slope.
- The minimum pitch for each roofing material is set by its maker.
Questions about this tool
What does 6 in 12 mean?
The roof rises 6 units for every 12 horizontal units, about 26.57 degrees or a 50% slope.
How do I measure pitch on site?
Hold a level horizontally on the roof and measure the vertical distance from its far end down to the roof surface.
What is the rafter factor for?
Multiply a horizontal run by it to get the true sloped length of the rafter or sheet.