Roof Pitch Calculator: Rise and Run to Degrees
Choose whether you know the rise and run or the roof angle. You get the angle, the x:12 pitch used by builders, the slope as a percent and the slope factor for working out roof area and rafter length.
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Formula
angle = atan(rise / run)pitch x:12 = 12 x rise / runslope percent = 100 x rise / runslope factor = sqrt(1 + (rise / run)^2) = 1 / cos(angle)- From an angle:
rise / run = tan(angle)
Rise and run must use the same unit. Only the ratio matters.
Worked example
Rise 6 and run 12: the ratio is 0.5. The angle is atan(0.5) = 26.57 degrees, the pitch is 6:12, the slope is 50 percent and the slope factor is sqrt(1.25) = 1.118.
From 30 degrees: tan 30 = 0.57735, so the pitch is 6.93:12, the slope is 57.74 percent and the slope factor is 1.1547.
Frequently asked questions
What does a 6:12 roof pitch mean?
It rises 6 units for every 12 units of horizontal run. The angle is atan(6 / 12) = 26.57 degrees and the slope is 50 percent.
How do I convert a roof angle to pitch?
Multiply the tangent of the angle by 12. For 30 degrees, tan 30 = 0.5774, so the pitch is 12 x 0.5774 = 6.93:12 and the slope is 57.74 percent.
What is the slope factor used for?
It is the length of the sloped surface per unit of run, sqrt(1 + (rise / run)^2). Multiply a footprint area or a horizontal run by it to get roof area or rafter length. A 6:12 pitch has a factor of 1.118.
What is a low-slope and a steep roof pitch?
Pitches below about 4:12 (18.4 degrees) are usually called low slope and often need special roofing materials. Pitches above 9:12 (36.9 degrees) are steep. Product limits vary, so follow the manufacturer's minimum pitch.