Roof Pitch Calculator
Your estimate
- Angle
- 26.57°
- Slope
- 50%
- Pitch multiplier
- 1.12
Convert between rise/run, x/12 pitch, angle and percent — and get the multiplier for roof area and rafters.
Updated 2026-10-20 · Based on: roof-pitch geometry and 3 shingle bundles per square.
How to use the Roof Pitch Calculator
- Measure the rise over 12 in of run with a level and tape, or enter a known angle or pitch.
- Read the pitch (x/12), angle and percent.
- Multiply the flat footprint by the pitch multiplier to get the real roof area.
Formula
Pitch = rise per 12 in of run. Angle = arctan(rise ÷ run). Multiplier = √(1 + (pitch ÷ 12)²).
A 6/12 roof is 26.57° with a multiplier of 1.12.
Worked example
With the values preset in the calculator above: (Rise & run)
- Riser height
- 6 in
- Tread depth
- 12 in
- Pitch
- 6/12 (6:12)
- Angle
- 26.57°
- Slope
- 50%
- Pitch multiplier
- 1.12
How to measure roof pitch
Hold a 12 in level horizontally against a rafter or the roof surface, with one end touching. Measure straight up from the other end of the level to the roof: that number of inches is the pitch — 6 in means a 6/12 roof. From the ground you can also measure the rise and the half-span of a gable and divide.
Roof pitch chart
| Roof pitch | Angle | Slope | Pitch multiplier |
|---|---|---|---|
| 1 | 4.76° | 8.33% | 1 |
| 2 | 9.46° | 16.67% | 1.01 |
| 3 | 14.04° | 25% | 1.03 |
| 4 | 18.43° | 33.33% | 1.05 |
| 5 | 22.62° | 41.67% | 1.08 |
| 6 | 26.57° | 50% | 1.12 |
| 7 | 30.26° | 58.33% | 1.16 |
| 8 | 33.69° | 66.67% | 1.2 |
| 9 | 36.87° | 75% | 1.25 |
| 10 | 39.81° | 83.33% | 1.3 |
| 12 | 45° | 100% | 1.41 |
Related guides
Frequently asked questions
What is the most common roof pitch?
Between 4/12 and 9/12 on houses; 6/12 is very common. Below 2/12 counts as a low-slope roof and needs membrane roofing instead of shingles.
How many degrees is a 4/12 pitch?
18.43°.
What is the minimum pitch for shingles?
2/12 with a double underlayment; 4/12 and steeper with standard underlayment.
More calculators
Estimates only — check quantities with your supplier and local building code before you order.