Roof Pitch Calculator
Enter rise and run (feet, inches or a mix like 5' 6"), an angle, or a pitch. Get the pitch in x/12, degrees, percent grade and the rafter factor, plus the roof area of your building.
Roof pitch
5/ 12
- Angle
- 22.62°
- Percent grade
- 41.7%
- Ratio
- 1 : 2.4
- Rafter factor
- 1.0833
- Hip/valley factor
- 1.4743
- Nearest ¼ pitch
- 5/12
- Roof area
- 1,365 ft²
- Roofing squares
- 13.7
Roof area assumes a simple gable or hip roof: footprint with overhangs × rafter factor. Add 10–15% for shingle waste.
What "6 in 12" actually means
Pitch is a framing-square number: for every 12 inches you move in, the roof climbs this many inches. Drag the rise and see the triangle, the angle and the extra length of sloped roof (the rafter factor) change together.
At 6/12 every foot of level floor below needs 1.118 ft of rafter and roofing above it. That multiplier is why a steep roof costs more to shingle than its footprint suggests: 12/12 needs 41% more material than a flat roof over the same house.
Roof pitch to degrees chart
| Pitch | Angle | Percent | Rafter factor | Hip/valley factor |
|---|---|---|---|---|
| 1/12 | 4.76° | 8.3% | 1.003 | 1.417 |
| 2/12 | 9.46° | 16.7% | 1.014 | 1.424 |
| 3/12 | 14.04° | 25% | 1.031 | 1.436 |
| 4/12 | 18.43° | 33.3% | 1.054 | 1.453 |
| 5/12 | 22.62° | 41.7% | 1.083 | 1.474 |
| 6/12 | 26.57° | 50% | 1.118 | 1.5 |
| 7/12 | 30.26° | 58.3% | 1.158 | 1.53 |
| 8/12 | 33.69° | 66.7% | 1.202 | 1.563 |
| 9/12 | 36.87° | 75% | 1.25 | 1.601 |
| 10/12 | 39.81° | 83.3% | 1.302 | 1.641 |
| 11/12 | 42.51° | 91.7% | 1.357 | 1.685 |
| 12/12 | 45° | 100% | 1.414 | 1.732 |
| 13/12 | 47.29° | 108.3% | 1.474 | 1.781 |
| 14/12 | 49.4° | 116.7% | 1.537 | 1.833 |
| 15/12 | 51.34° | 125% | 1.601 | 1.887 |
| 16/12 | 53.13° | 133.3% | 1.667 | 1.944 |
| 17/12 | 54.78° | 141.7% | 1.734 | 2.002 |
| 18/12 | 56.31° | 150% | 1.803 | 2.062 |
| 19/12 | 57.72° | 158.3% | 1.873 | 2.123 |
| 20/12 | 59.04° | 166.7% | 1.944 | 2.186 |
| 21/12 | 60.26° | 175% | 2.016 | 2.25 |
| 22/12 | 61.39° | 183.3% | 2.088 | 2.315 |
| 23/12 | 62.45° | 191.7% | 2.162 | 2.382 |
| 24/12 | 63.43° | 200% | 2.236 | 2.449 |
Pitch, slope and angle
Carpenters say pitch or slope for rise per 12" of run (6/12, "six in twelve"). Strictly, old texts define pitch as rise over the full span, so a 6/12 slope is a "1/4 pitch"; you will still see that on old plans. Angle in degrees is arctan(rise ÷ run). Percent grade is rise ÷ run × 100, the number surveyors and civil drawings use.
Once you know the pitch, the rafter calculator gives rafter length, birdsmouth and ridge height.
Ask the shop
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