Free contractor tool
Roof Pitch Calculator
Enter vertical rise and horizontal run in inches to convert roof slope to x:12, degrees and percent. Add horizontal projected area for a simple uniform-slope area calculation.
These are example inputs, not recommended prices or a job assessment. Replace them with your own figures.
Your result
- Rise per 12 inches of run
- 6:12
- Angle (degrees)
- 26.565°
- Slope (%)
- 50%
- Area multiplier
- 1.11803
- Sloped area (sq ft)
- 1,118.03
- Roofing squares (100 sq ft each)
- 11.18
Area assumes one uniform slope over the entered horizontal projected area. It excludes waste, laps, overhangs and roof details. This is geometry, not a material specification or structural check.
Calculations stay in this browser. No signup or email is needed.
How the calculation works
Rise per 12 inches is 12 × rise ÷ horizontal run. The angle is arctan(rise ÷ run). Slope percent is 100 × rise ÷ run. The sloped-area multiplier is the square root of 1 + (rise ÷ run)².
For example, a 6-inch rise over a 12-inch run is 6:12, 50% slope and approximately 26.565 degrees. Its area multiplier is about 1.11803. A 1,000 sq ft horizontal projection at that uniform slope gives about 1,118.03 sq ft, before any added allowance.
Run is horizontal, not the distance along the roof
The tool uses horizontal run, not total building span or a measurement along the sloped surface. Both rise and run must use the same unit. The area input is a horizontal projection in square feet.
This does not measure a roof, specify shingles or decide whether a material is suitable. It does not account for hips, valleys, openings, overhangs, waste or structural loads. Use verified measurements and the applicable design and product instructions.