Enter the roof pitch as inches of rise per 12 inches of run, such as 6 for a 6-in-12 roof. Measure it with a level and a tape, or read it from the plans. The tool converts to the slope angle in degrees using the arctangent of pitch over 12, and to a percent grade.
A 12-in-12 roof is 45 degrees and a 100% grade.
Roof surface area is larger than the footprint by a pitch multiplier, which the roofing calculator accounts for. Measuring pitch on a real roof is hazardous. Percent grade and angle are different: 100% is 45 degrees, not 100 degrees.
Manufacturers state minimum pitches for their products.
Roof angle (degrees) from roof pitch (rise per 12)
| Roof pitch (rise per 12) | 6 |
|---|---|
| Roof angle (degrees) | 26.6 |
| Slope | 50.0% |
Common error: Confusing pitch with percent slope. A 6 in 12 pitch is a 50 percent slope, and mixing the two gives a very different angle.
Roof Pitch & Angle: formula
Roof Pitch & Angle: changing Roof pitch (rise per 12)
| Roof pitch (rise per 12) | Roof angle (degrees) | Slope |
|---|---|---|
| 4.8 | 21.8 | 40.0% |
| 5.4 | 24.2 | 45.0% |
| 6 (example) | 26.6 | 50.0% |
| 6.6 | 28.8 | 55.0% |
| 7.2 | 31 | 60.0% |
Roof Pitch & Angle: compare input ranges
| Input | Tested from | To | Roof angle (degrees): low input | Roof angle (degrees): high input | Swing |
|---|---|---|---|---|---|
| Roof pitch (rise per 12) | 5.4 | 6.6 | 24.2 | 28.8 | 4.6 (17%) |
Roof Pitch & Angle: individual input comparisons
| Input | Value | Roof angle (degrees) | Slope |
|---|---|---|---|
| Roof pitch (rise per 12) | 4.8 | 21.8 | 40.0% |
| 5.4 | 24.2 | 45.0% | |
| 6 | 26.6 | 50.0% | |
| 6.6 | 28.8 | 55.0% | |
| 7.2 | 31 | 60.0% |
Roof Pitch & Angle: values and definitions
| Quantity and definition | Value used |
|---|---|
| Roof pitch (rise per 12) — Roof pitch, in inches of rise per 12 inches of run. | 6 |
| Roof angle (degrees) | 26.6 |
| Slope | 50.0% |
Roof pitch (rise per 12): half and double
| Roof pitch (rise per 12) | Roof angle (degrees) |
|---|---|
| 3 | 14 |
| 6 | 26.6 |
| 12 | 45 |
Roof pitch is stated as rise per 12 inches of run, and it converts to an angle and a slope. A 6 in 12 roof rises 6 inches for every 12 inches across, which is an angle of about 26.6 degrees and a slope of 50 percent. A 12 in 12 roof is 45 degrees.
The pitch decides which roofing materials are allowed, how fast water sheds and how much roof surface a given footprint has.
Check the minimum pitch for the roofing you plan to use. Some materials need a steeper slope or a special underlayment on a low one.
Estimate material on the roofing calculator, rafter length on the rafter length page and the geometry on the right triangle and trigonometry calculators. The distance and slope and stair stringer calculators use similar slope math, and the deck and drain slope pages relate to grades.
What is the minimum pitch for asphalt shingles?
Check the selected shingle manufacturer’s minimum slope and low-slope underlayment instructions; this geometric result does not specify an assembly.
Is a 12-in-12 roof 45 degrees?
Yes. Equal rise and run give a 45 degree angle and a 100% grade.