How do you calculate roof height from the pitch?
Short answer. Roof height (rise) equals the run times the pitch divided by 12. For a symmetrical gable, the run is half the building's width: a 28 foot wide house with an 8/12 pitch has a 14 foot run and rises 14 × 8 ÷ 12 = 9.33 feet, about 9 feet 4 inches, from the top of the walls to the ridge line.
The formula
Rise = run × (pitch ÷ 12)
Use run in feet to get rise in feet.
Worked examples
- 24 foot wide garage, 6/12: run 12 feet, rise 12 × 0.5 = 6 feet.
- 30 foot wide house, 7/12: run 15 feet, rise 15 × 0.583 = 8.75 feet (8 feet 9 inches).
- 36 foot wide house, 10/12: run 18 feet, rise 18 × 0.833 = 15 feet.
Working backward: pitch from height
Pitch = (rise ÷ run) × 12. If you know the ridge is 10 feet above the wall tops on a 30 foot wide house, run is 15, so 10 ÷ 15 × 12 = 8. That is an 8/12 pitch.
Details that change the real height
- The formula gives the height of the roof line above the outside top of the wall. Actual ridge height also depends on rafter or truss depth and heel height.
- Total height above the ground adds the wall height and foundation.
- On a hip roof with equal pitches, rise is the same as for a gable of the same width, but the ridge is shorter.
- Unequal pitches or offset ridges need each side calculated separately.
Why homeowners ask
Height matters for HOA and zoning limits, for adding a bonus room, and for planning ladder access. For the vocabulary of rise, run and span, see roof anatomy explained, and for measuring the existing roof, how roofers measure a roof.