Roof pitch, slope and angle all describe how steep a roof is. US roofers use pitch (rise in inches per 12 inches of run). Phone apps, plans from outside the US and many product sheets use degrees. This chart converts between them, so you never have to guess.
Roof pitch to degrees chart
| Pitch | Angle | Slope % | Rise per foot | Walkability |
|---|---|---|---|---|
| 1/12 | 4.76° | 8.3% | 1 in | Low slope, not for shingles |
| 2/12 | 9.46° | 16.7% | 2 in | Low slope |
| 3/12 | 14.04° | 25.0% | 3 in | Low slope |
| 4/12 | 18.43° | 33.3% | 4 in | Easy to walk |
| 5/12 | 22.62° | 41.7% | 5 in | Easy to walk |
| 6/12 | 26.57° | 50.0% | 6 in | Walkable with care |
| 7/12 | 30.26° | 58.3% | 7 in | Walkable with care |
| 8/12 | 33.69° | 66.7% | 8 in | Steep, use roof jacks |
| 9/12 | 36.87° | 75.0% | 9 in | Steep, use roof jacks |
| 10/12 | 39.81° | 83.3% | 10 in | Very steep, harness |
| 11/12 | 42.51° | 91.7% | 11 in | Very steep, harness |
| 12/12 | 45.00° | 100% | 12 in | Very steep, harness |
| 14/12 | 49.40° | 116.7% | 14 in | Extreme |
| 16/12 | 53.13° | 133.3% | 16 in | Extreme |
| 18/12 | 56.31° | 150.0% | 18 in | Extreme |
| 24/12 | 63.43° | 200.0% | 24 in | Extreme |
The walkability column is a rule of thumb for a dry roof in good shoes. Federal OSHA rules treat any roof steeper than 4/12 as a steep roof for fall protection, so pros use harnesses or roof jacks well before a roof “feels” steep.
The formula, in plain words
The pitch is a right triangle: 12 inches across (run) and the rise going up.
- Pitch to degrees: angle = arctan(rise ÷ 12)
- Degrees to pitch: rise = 12 × tan(angle)
- Slope percent: rise ÷ 12 × 100
Worked example: degrees from a phone app
Your phone’s level app reads 30° on the rafter.
- tan(30°) = 0.577
- 0.577 × 12 = 6.93
- Round to the nearest whole number: 7/12 pitch
You can skip the math. Type 30 into the Pitch angle box of the roof square footage calculator and it converts the angle and uses it for the area.
Why the angle matters for roof area
A steeper roof covers more surface than its flat footprint. The extra area grows slowly at first and then fast:
| Pitch | Angle | Extra area vs flat |
|---|---|---|
| 4/12 | 18.43° | +5.4% |
| 6/12 | 26.57° | +11.8% |
| 8/12 | 33.69° | +20.2% |
| 10/12 | 39.81° | +30.2% |
| 12/12 | 45.00° | +41.4% |
So the same 1,500 sq ft footprint needs 1,581 sq ft of shingles at 4/12 but 2,121 sq ft at 12/12. That is why the pitch is the single biggest input after length and width. The full multiplier chart is on the calculator page.
Common conversion mistakes
- Reading the angle off the shingles. Shingle courses add a small bump. Measure on a rafter, the fascia board or a straight board laid across several courses.
- Mixing up pitch and angle. A “6 degree” roof is nearly flat (about 1.3/12). A “6 pitch” roof is 26.6°.
- Rounding too early. 7/12 is 30.26°, not 30°. For area, that difference on a 2,000 sq ft footprint is only about 6 sq ft, but rounding pitch by a whole number (6 vs 7) changes the area by about 80 sq ft.
- Using the wrong run. Pitch always uses 12 inches of horizontal run, not 12 inches along the slope.
Not sure what your pitch is yet? Here are three ways to measure roof pitch without climbing. If you just want the typical range for houses and sheds, see standard roof pitch.