Roof pitch calculator
Convert roof pitch between X/12, degrees and percent. Add the building width and length to see the ridge height, rafter length and area of a gable roof.
See your design as an AI render — free- In degrees
- 26.57°
- As X/12
- 6/12
- Ridge height
- 6 ft
- Rafter length (no overhang)
- 13.42 ft
- Roof area (gable)
- 1,073.3 sq ft
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How to calculate roof pitch
Pitch compares how much the roof rises with how far it runs horizontally.
- 1
Divide the rise by the run
Pitch = rise ÷ run. A roof that rises 6 in for every 12 in of run is 6 ÷ 12 = 0.5, or 50%: a 6/12 pitch.
- 2
Convert to degrees
The angle is the arctangent of the pitch. 6/12 is 26.57°. The other way round, 45° is 12/12, or 100%.
- 3
Convert to percent or X/12
Percent = pitch × 100, and X/12 = pitch × 12. A 30% roof is 3.6/12.
- 4
Work out ridge, rafter and area
On a gable roof with the ridge in the middle, the ridge rises half the width × pitch: 24 ft wide at 6/12 gives 6 ft. The rafter, without overhang, is 13.42 ft, and both slopes over a 40 ft length cover about 1,073 sq ft.
Roof pitch conversions
Common X/12 pitches as percent and degrees.
| X/12 | Percent | Degrees |
|---|---|---|
| 2/12 | 16.7% | 9.5° |
| 3/12 | 25% | 14° |
| 4/12 | 33.3% | 18.4° |
| 6/12 | 50% | 26.6° |
| 8/12 | 66.7% | 33.7° |
| 9/12 | 75% | 36.9° |
| 12/12 | 100% | 45° |
Frequently asked questions
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