Roof Pitch Calculator
Roof pitch is how steep a roof is, written in the US as rise over run — inches of rise per 12 inches of run, like 6:12. Enter the rise and run to get the pitch, the angle, and the factor that turns a floor plan into actual roof area.
Your numbers
Result
- Angledegrees
- 26.57
- Percent slope%
- 50
- Slope factor× footprint = roof area
- 1.12
| Measure | Value |
|---|---|
| Pitch (rise:run) | 6:12 |
| Angle | 26.6° |
| Percent slope | 50.0% |
| Slope factor (× footprint) | 1.118 |
What "rise over run" means
Pitch is the rise (how far the roof goes up) over the run (how far it goes across), stated per 12 inches of run. A roof that rises 6 inches for every 12 of run is a "6:12" pitch. The calculator scales any rise and run to the /12 form and also gives the angle in degrees and the percent slope.
From footprint to roof area
A sloped roof has more surface than the floor below it. The slope factor is √(run² + rise²) ÷ run — multiply your building's footprint by it to get the true roof area. A 6:12 pitch has a factor of about 1.118, so the roof is ~12% larger than the plan. This is the number you need to order shingles.
Common pitches
Flat-ish roofs run 2:12 to 4:12; a typical residential roof is 4:12 to 9:12; anything past 9:12 is steep and harder (and less safe) to walk. Very low slopes need special membranes rather than shingles. The pitch also affects drainage, snow shedding and how a house looks.
Frequently asked questions
Sources
- Roof pitch geometry (rise:run, slope factor)
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