Roof Pitch & Rafter Calculator
Pitch angle and rafter length from the rise and run you measure.
Pitch angle and rafter length from the rise and run you measure. The slope factor turns a plan length into a sloped length.
Measure
Pitch
16.7°
A rise of 300 mm over 1,000 mm is 16.7°. The rafter along that triangle is 1,044 mm.
- Rafter
- 1,044 mm
- Slope factor
- 1.044
- Multiply a plan length by the slope factor to get the sloped length.
- This is geometry, not a structural design.
Pitch16.7°
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Worked example
A rise of 300 mm over a run of 1,000 mm is a pitch of about 16.7 degrees. The rafter along that triangle is about 1,044 mm, and the slope factor is 1.044 — once you have that, plan lengths turn into sloped lengths.
FAQ
- What are rise and run?
- Rise is the vertical height. Run is the horizontal distance. You can type millimetres, metres, or feet.
- What is the slope factor?
- Rafter length divided by run. Multiply a plan length by the factor to get the sloped length.
- Is this a structural design?
- No. It’s the geometry of the triangle. Check spans and members separately.