Roof pitch calculator
Have a rise and a run, or an angle? Convert them into the same roof pitch.
Free to use. No registration. No uploads.
Your pitch conversion
Assumes a straight, uniform roof plane. Run is horizontal distance, never the sloped rafter length.
Estimates only. Verify measurements and product requirements before use.
How the conversion works
Angle = arctan(rise ÷ run)
Percent slope = 100 × rise ÷ run
A rise of 3 ft over a horizontal run of 6 ft gives 12 × 3 ÷ 6 = 6, or 6/12. The angle is arctan(0.5) = 26.565051°. Percent slope is 50%. In reverse, 12 × tan(26.565051°) returns a rise of 6 per 12.
The geometric factor is √(1 + (rise ÷ run)²), or 1.118034 for this example. Values above 120/12 (about 84.29°) are outside this planning tool’s range.
View the pitch factor tablePitch questions
Is roof pitch the same as degrees?
Both describe slope, but use different scales. A 6/12 pitch is approximately 26.565 degrees, not 6 degrees.
What is the run?
Run is the horizontal distance corresponding to the rise. For a symmetric gable from eave to ridge, it is half the horizontal span. Do not enter the rafter length.
Can rise and run be in different units?
No. Convert them to the same unit first. The feet/meters switch converts both values together.
What does a 100% slope mean?
Rise equals run: 12/12, a 45 degree angle and a factor of about 1.414214. Percent slope is not angle in degrees.
How do I measure safely?
Use a known plan or an accessible, level-ground measurement. Do not climb onto a roof to obtain calculator inputs. Ask a qualified roofer if pitch is uncertain.