Roof Slope Converter
Last reviewed How we calculate
Roof slope is written in three common ways: as a pitch such as 6 in 12, as an angle in degrees, and as a percent grade. Plans, product sheets and building codes do not always use the same one. This converts between them and gives the pitch multiplier as well.
Pitch, degrees and percent
Convert roof slope between pitch, degrees and percent, with the pitch multiplier.
This calculator needs JavaScript to work. The measurements below are the ones you would need to do the sum by hand.
Pitch
- Angle
- Percent grade
- Pitch multiplier Sloped length for each unit of level run.
Below 2 in 12: a low-slope roof that needs a membrane rather than shingles.
From 2 in 12 up to 4 in 12: shingles are allowed with a double layer of underlayment.
At 4 in 12 and steeper: standard shingle installation applies.
Pitch, degrees and percent all describe the same slope. Roofers in North America use pitch; building plans elsewhere often use degrees.
How the conversions work
A pitch is the rise in inches for 12 inches of run. The angle is the arctangent of the rise over 12, and the percent grade is the rise over 12 times 100. Going the other way, the pitch is 12 times the tangent of the angle, or the percent times 12 over 100.
Common slopes
A 4 in 12 roof is about 18.4 degrees or 33.3 per cent. 6 in 12 is about 26.6 degrees or 50 per cent. 8 in 12 is about 33.7 degrees or 66.7 per cent, and 12 in 12 is exactly 45 degrees or 100 per cent.
What the slope decides
Below 2 in 12 a roof needs a low-slope membrane. From 2 in 12 up to 4 in 12, shingles are allowed with a double layer of underlayment, and from 4 in 12 up, standard installation applies. The pitch multiplier turns a flat measurement into a sloped one, which is how the roof area calculator works.
Frequently asked questions
Is a 12 in 12 roof 45 degrees?
Yes. The rise equals the run, so the angle is exactly 45 degrees and the grade is 100 per cent.
What is percent grade on a roof?
The rise divided by the run, times 100. A 6 in 12 roof rises 6 for every 12 across, which is a 50 per cent grade.
What counts as a low-slope roof?
Roofs below 2 in 12 need low-slope coverings such as membranes. Between 2 and 4 in 12, shingles can be used with a double layer of underlayment.