What does a roof pitch conversion chart look like?
Short answer. A roof pitch conversion chart translates the x/12 pitch roofers use into degrees, percent grade, simple ratios and metric millimetres per metre. For example, 6/12 equals 26.6 degrees, 50 percent, a 1:2 ratio, and 500 mm per metre.
Conversion formulas
- Degrees = arctan(x ÷ 12)
- Percent = (x ÷ 12) × 100
- Ratio (rise:run) = x:12, reduced (6:12 = 1:2)
- Metric = (x ÷ 12) × 1,000 mm per metre
- Back to x/12 from degrees = 12 × tan(degrees)
Chart: pitch, degrees, percent, ratio
- 1/12: 4.8 degrees, 8.3 percent, 1:12
- 2/12: 9.5 degrees, 16.7 percent, 1:6
- 3/12: 14.0 degrees, 25 percent, 1:4
- 4/12: 18.4 degrees, 33.3 percent, 1:3
- 5/12: 22.6 degrees, 41.7 percent, 1:2.4
- 6/12: 26.6 degrees, 50 percent, 1:2
- 7/12: 30.3 degrees, 58.3 percent, 1:1.71
- 8/12: 33.7 degrees, 66.7 percent, 1:1.5
- 9/12: 36.9 degrees, 75 percent, 1:1.33
- 10/12: 39.8 degrees, 83.3 percent, 1:1.2
- 12/12: 45 degrees, 100 percent, 1:1
- 18/12: 56.3 degrees, 150 percent, 1.5:1
- 24/12: 63.4 degrees, 200 percent, 2:1
Common angle lookups
- 15 degrees is about 3.2/12
- 20 degrees is about 4.4/12
- 30 degrees is about 6.9/12
- 35 degrees is about 8.4/12
- 40 degrees is about 10.1/12
Notice that percent and degrees are not the same thing: a 100 percent grade is 45 degrees, not 90. Mixing them up is the most common conversion error. Building codes and shingle instructions in the US state minimum slopes in x/12, so convert to that before checking a product. See how roofers measure a roof.