Pitch is how many inches a roof rises for every 12 in it runs. A 6/12 roof rises 6 in per foot.
Roof pitch calculator
Enter the rise over any run. Add a horizontal run to get the rafter length.
Enter your numbers to see the result.
Pitch, angle and slope
- Pitch = rise / run x 12, written as x/12.
- Angle = arctan(rise / run).
- Slope % = rise / run x 100.
- Pitch factor = √(1 + (rise / run)²). Multiply plan area by it to get roof area.
| Pitch | Angle | Pitch factor |
|---|---|---|
| 3/12 | 14.0° | 1.031 |
| 4/12 | 18.4° | 1.054 |
| 6/12 | 26.6° | 1.118 |
| 8/12 | 33.7° | 1.202 |
| 10/12 | 39.8° | 1.302 |
| 12/12 | 45.0° | 1.414 |
Measuring pitch without a ladder
Hold a level against a rafter in the attic or along the gable end, measure 12 in along the level and then straight up to the underside of the rafter. That measurement is the rise.
Rafter length
A rafter covering a horizontal run of 15 ft on a 6/12 roof is 15 x 1.118 = 16.8 ft along the slope, before the overhang and the ridge cut.
Frequently asked questions
What angle is a 6/12 pitch?
About 26.6 degrees.
What is a 4/12 roof pitch?
A roof that rises 4 in for every 12 in of run, about 18.4 degrees.
Is a 12/12 roof 45 degrees?
Yes. Rise equals run, so the angle is 45 degrees.