Roof Pitch Calculator
Calculate roof pitch, slope angle, and slope multiplier from a roof's rise and horizontal run.
Rise and run must use the same unit.
Measure the vertical rise and horizontal distance, not the sloped rafter length.
Roof pitch
6:12rise : 12 run
Slope angle26.6°
Slope multiplier1.118
Rise / run ratio0.500
Pitch percentage50.0%
Use the slope multiplier to estimate sloped surface area from horizontal plan area for a uniform-pitch plane.
How to use the Roof Pitch Calculator
- Choose the unit you will use for both measurements.
- Enter the vertical rise and horizontal run.
- Select Calculate pitch to see the pitch ratio, angle, multiplier, and percentage.
Formula
Pitch per 12 = (rise ÷ run) × 12. Angle = arctan(rise ÷ run). Slope multiplier = √[1 + (rise ÷ run)²].
Assumptions and Limitations
This calculator assumes a single roof plane with a constant slope. It does not calculate total roof area or model hips, valleys, dormers, multiple roof pitches, or complex roof geometry. Measure rise and run on the same plane, and verify measurements before purchasing materials or planning work.
