Roof Pitch Calculator
Convert roof rise and run to pitch, angle, percent grade and the rafter length per foot of run.
Roof pitch
6.00 in 12
- Angle
- 26.57°
- Percent grade
- 50%
- Slope factor
- 1.118
- Rafter length per foot of run
- 13.42 in
A pitch of 6 in 12 is an angle of 26.6°, a grade of 50%, and a slope factor of 1.118. Multiply a horizontal distance by the slope factor to get the length along the roof.
Calculation breakdown
| Step | Formula | Result |
|---|---|---|
| Slope (rise ÷ run) | 6 ÷ 12 | 0.5 |
| Pitch (inches of rise per 12 in of run) | 0.5 × 12 | 6.00 in 12 |
| Angle | arctan(0.5) | 26.57° |
| Slope factor | √(1 + (6 ÷ 12)²) | 1.118 |
How it works
Choose what you know: the rise and run, the pitch or the angle. The calculator converts it into all the others.
Worked example
A roof that rises 6 inches over a 12 inch run:
- Slope: 6 ÷ 12 = 0.5
- Pitch: 0.5 × 12 = 6 in 12
- Angle: arctan(0.5) = 26.57°
- Percent grade: 50%
- Slope factor: √(1 + 0.5²) = 1.118, which is 13.42 inches of rafter per foot of run
Rounding
Angles and factors are shown to two to four decimal places. Calculations use the unrounded values.
Sources
Frequently asked questions
How do you calculate roof pitch?
Divide the rise by the run and multiply by 12. Roof pitch is the inches of rise per 12 inches of horizontal run, so a roof that rises 6 inches over 12 inches of run has a 6/12 pitch. Measure rise and run in the same unit and the unit cancels out.
What angle is a 6/12 roof pitch?
A 6/12 pitch is an angle of 26.57 degrees, a grade of 50%. Swanson Tool Co. lists 26.6 degrees for 6/12. You find the angle with the arctangent of the rise divided by the run.
What is the slope factor?
The slope factor is the square root of 1 plus the squared slope. It converts a horizontal distance into a length along the roof, which is 1.118 for a 6/12 pitch. Multiply the factor by 12 to get the rafter length in inches per foot of run, 13.42 inches at 6/12.
How do I convert degrees to roof pitch?
Take the tangent of the angle and multiply by 12. A 45 degree roof has a tangent of 1, so its pitch is 12/12. Choose the Angle option in the calculator to convert any angle up to 75 degrees.
What is a roof slope calculator?
It is the same tool. Roof slope and roof pitch both describe how steep a roof is, written as a ratio like 6/12, as an angle in degrees or as a percent grade. This calculator shows all of them at once.
Estimates only. Measure the actual roof and check local code and your roofing supplier before ordering materials.