Free tool
Roof pitch & slope calculator
Roof pitch is how many inches a roof rises for every 12 inches of horizontal run. A 6/12 roof rises 6 in per 12 in, which is 26.57° or a 50% slope. Type any one value below (pitch, degrees, percent or rise and run) and the calculator converts it to the others.
The maths
- Slope is rise ÷ run. A pitch of 6/12 is 6 ÷ 12 = 0.5.
- Percent is that slope × 100: 0.5 is a 50% slope.
- Degrees is the arctangent of the slope: arctan(0.5) ≈ 26.57°.
- Pitch is the slope × 12, written over 12: 0.5 × 12 = 6/12.
The International Residential Code writes roof slopes the same way, as units vertical in 12 units horizontal, sometimes with the percent alongside, as in “2 units vertical in 12 units horizontal (17-percent slope)” (ICC, 2024 IRC §R905.2.2). What slope a particular roof covering needs is set by the code where you live and the manufacturer, so check with them; this page only converts numbers.
Common pitches
| Pitch | Degrees | Percent |
|---|---|---|
| 1/12 | 4.76° | 8.3% |
| 2/12 | 9.46° | 16.7% |
| 3/12 | 14.04° | 25.0% |
| 4/12 | 18.43° | 33.3% |
| 5/12 | 22.62° | 41.7% |
| 6/12 | 26.57° | 50.0% |
| 7/12 | 30.26° | 58.3% |
| 8/12 | 33.69° | 66.7% |
| 9/12 | 36.87° | 75.0% |
| 10/12 | 39.81° | 83.3% |
| 11/12 | 42.51° | 91.7% |
| 12/12 | 45.00° | 100.0% |
Questions
What does a 6/12 roof pitch mean?
The roof rises 6 inches for every 12 inches it runs horizontally. That is a slope of 50% and an angle of about 26.57°.
How do I convert roof pitch to degrees?
Divide the rise by 12, then take the arctangent. For a 4/12 pitch: arctan(4 ÷ 12) ≈ 18.43°. The calculator does it for any pitch.
Is percent slope the same as degrees?
No. Percent slope is rise ÷ run × 100, so a 45° slope is 100%. The building code writes slopes both ways, for example “2 units vertical in 12 units horizontal (17-percent slope)” (ICC, 2024 IRC §R905.2.2).
Can my phone measure a slope?
Yes, for a surface you can reach safely. Lay the phone on it with the level in Surface mode, or use the Angle tool in The Measure App on a corner you can see. Readings are approximate.