Sixteenth
Roof Pitch Calculator
Enter any two of rise, run, diagonal, pitch or angle. The calculator solves the rest of the right triangle, so it works for roofs, ramps, stairs and braces.
Fill in any two boxes and leave the rest empty. Pitch and angle together are not enough: add a length.
Pitch, angle and slope
Roof pitch is the rise in inches for every 12" of level run. The same triangle gives the angle, the grade and the slope factor.
pitch = rise ÷ run × 12 · angle = atan(rise ÷ run)
diagonal = √(rise² + run²) · grade = rise ÷ run × 100%
| Pitch | Angle | Grade | Slope factor |
|---|---|---|---|
| 2/12 | 9.5° | 16.7% | 1.014 |
| 3/12 | 14.0° | 25% | 1.031 |
| 4/12 | 18.4° | 33.3% | 1.054 |
| 5/12 | 22.6° | 41.7% | 1.083 |
| 6/12 | 26.6° | 50% | 1.118 |
| 7/12 | 30.3° | 58.3% | 1.158 |
| 8/12 | 33.7° | 66.7% | 1.202 |
| 9/12 | 36.9° | 75% | 1.250 |
| 10/12 | 39.8° | 83.3% | 1.302 |
| 12/12 | 45.0° | 100% | 1.414 |
Questions
How do I find the pitch of a roof?
Measure how much the roof rises over 12" of level run. If it rises 6" in 12", the pitch is 6/12. You can also measure any rise and run: pitch = rise ÷ run × 12.
How do I convert roof pitch to degrees?
Angle = atan(pitch ÷ 12). 4/12 is 18.4°, 6/12 is 26.6°, 8/12 is 33.7°, 12/12 is 45°.
What is the slope factor?
The length of the roof per foot of run: √(12² + pitch²) ÷ 12. Multiply a run by it to get the sloped length. For 6/12 it is 1.118.