RoofPitch · geometry construction
RoofPitch roof pitch geometry
Express a measured rise/run as angle, percent, and x:12 before ordering roofing or discussing slope
Result
angle=atan(rise/run); slope%=100*rise/run; pitch_in_12=12*rise/run
How to use this estimate
Convert roof rise and run into pitch angle (degrees), percent slope, and X-in-12 pitch. How it works: angle=atan(rise/run); slope%=100*rise/run; pitch_in_12=12*rise/run. Out of scope: rafter sizing; snow load; underlayment requirements; hip/valley compound cuts; roof surface area from footprint. Informational calculation for the stated inputs only. Does not certify code compliance; confirm manufacturer data where it applies.
Sources, methodology, and assumptions
Methodology
angle=atan(rise/run); slope%=100*rise/run; pitch_in_12=12*rise/run
Assumptions
Rise and run measured on the same right triangle; Run>0. Informational calculation for the stated inputs only.
Out of scope
rafter sizing; snow load; underlayment requirements; hip/valley compound cuts; roof surface area from footprint
Sources
Last technically reviewed: 2026-09-11