Roof Pitch Calculator
Find roof pitch, angle and slope factor from rise and horizontal run.
Loading calculator…
What this tool does
Find roof pitch, angle and slope factor from rise and horizontal run. Horizontal run is not the slope distance.
How to use the Roof Pitch Calculator
- Enter or select roof rise in in.
- Enter or select horizontal run in in.
- Read the calculated result; change any measurement to compare alternatives.
Formula
pitch=12×rise/run; angle=atan(rise/run)×180/π
- rise
- Roof rise (in, before metric conversion)
- run
- Horizontal run (in, before metric conversion)
Horizontal run is not the slope distance.
Worked example
For roof pitch calculator, the following measurements illustrate the exact method: Roof rise: 6; Horizontal run: 12.
Inputs
- Roof rise6 in
- Horizontal run12 in
Result
- Pitch (rise per 12)6
- Roof angle (degrees)26.57
- Slope factor1.12
Results explained
- Pitch (rise per 12)
- Pitch (rise per 12) from the formula above. Horizontal run is not the slope distance.
- Roof angle (degrees)
- Roof angle (degrees) from the formula above. Horizontal run is not the slope distance.
- Slope factor
- Slope factor from the formula above. Horizontal run is not the slope distance.
Frequently asked questions
Rise divided by run multiplied by 12 gives the conventional pitch.
Measure vertical rise and horizontal run in matching units.
Use 5–10% for simple layouts and 10–15% for diagonal cuts or complicated outlines; the allowance is editable.
Split the outline into rectangles or triangles and calculate each section separately. Do not count overlapping sections twice.
This is a purchasing estimate, not a structural design. Confirm measurements and local requirements before buying or building.