Roof pitch calculator
Convert roof rise and run into pitch, angle and slope length. Start with measurements, a pitch per 12 or an angle.
Nonnegative slopes from 0 to 89.9 degrees. One straight roof plane; vertical roofs and negative slopes are outside this calculator. This is geometry, not a material or building-code approval. Change the input or settings to update your result. Results update as you type. Up to 1,000,000 characters.
Your result
How to use Roof pitch calculator
- Choose rise/run, pitch per 12 or angle as your input.
- Enter the horizontal run and its unit.
- Compare pitch, slope length and angle, then download the conversion.
Useful next steps
Use horizontal run
Run is the horizontal distance for one roof plane. It is not the length along the slope. For a symmetric roof it is typically half the horizontal span, before separately accounting for overhang. Enter run in every mode so the result can also show rise and slope length.
Convert the measurement you have
Choose Rise and run, Pitch per 12 or Angle. Pitch per 12 means vertical rise for every 12 units of horizontal run. A 3 metre rise over a 4 metre run is 9-in-12, a 75% slope and an angle of about 36.87 degrees. Its straight slope length is 5 metres.
Read the area multiplier
For a uniform planar slope, the multiplier is slope length divided by horizontal run. Multiplying the horizontal plan area by that value gives the corresponding sloped area. Roof intersections, openings and overhangs still need their own measurements.
Keep geometry separate from design
Download CSV, text or JSON calculations. The result does not select a roof material, establish a minimum permitted slope or size a structural rafter. Cuts, ridge deductions and construction details are excluded.