How to calculate roof pitch
Measure rise and run in the same units, then scale the result to a 12 inch run. A 6 inch rise over 12 inches of run is a 6/12 roof pitch.
Pitch, slope, and angle are related
Roof pitch is usually written as rise over 12. Slope can also be shown as percent or angle. For example, 4/12 is about 18.4 degrees and 6/12 is about 26.6 degrees.
Measure safely
Use building plans, attic measurements, or ground-level methods when possible. Do not climb onto an unsafe roof to collect measurements for a calculator.
Common roof pitch checks
Pitch is rise per 12 inches of run. Use plans or safe measurements; do not climb onto unsafe roofs for calculator inputs.
| Pitch | Approx. angle | Area multiplier |
|---|---|---|
| 4/12 | 18.4 degrees | 1.054x footprint |
| 6/12 | 26.6 degrees | 1.118x footprint |
| 8/12 | 33.7 degrees | 1.202x footprint |
| 12/12 | 45 degrees | 1.414x footprint |
Before you calculate
- Measure rise and run consistently, commonly using inches of rise over 12 inches of run.
- Use the same roof section for both measurements.
- Check separate roof planes when the roof has more than one pitch.
Common mistakes
- Confusing pitch ratio, slope percentage, and angle degrees.
- Measuring along the roof surface instead of using rise and horizontal run.
- Applying one pitch to a roof with multiple planes.
Formula
pitch = (rise / run) * 12
Assumptions
- Pitch is a geometry relationship, not a material quantity.
- Use safe ground-level or plan measurements whenever possible.
- Roof material quantities still need roof area, waste, and product coverage.
Example
Estimated roof pitch: 12 in 12 pitch
How to calculate roof pitch
- Enter roof rise and run in the same units.
- Convert the rise/run relationship into inches of rise per 12 inches of run.
- Review the pitch ratio, slope percentage, and angle when the calculator provides them.
- Use plans, attic framing, or safe ground-level measurements instead of climbing onto an unsafe roof.
- Use roof area, material coverage, and waste separately when estimating roofing materials.
Before you buy materials
- Use pitch results as context for material planning, not as a final roof measurement.
- Verify roof pitch safely from plans or with a qualified roofer when access is risky.
FAQ
What is the example 12/12 roof pitch in 12 pitch result?
Use roof rise, roof run, then calculate the planning result. In the default example, the result is 12 in 12 pitch.
What is a 6/12 roof pitch?
A 6/12 pitch means the roof rises 6 inches for every 12 inches of horizontal run. It is about 26.6 degrees.
How do I convert roof pitch to angle?
Use angle = arctangent(rise / run). For a 4/12 pitch, arctangent(4 / 12) is about 18.4 degrees.
Does roof pitch calculate roof area?
No. Pitch is a slope relationship. Roof material quantity still needs roof area, waste, and product coverage.
Should I climb on the roof to measure pitch?
No. Use plans, attic framing, or a qualified roofer when measurements cannot be taken safely.
Related calculators
This calculator is for planning estimates only. Verify final quantities with product labels, project conditions, and a qualified professional when accuracy matters.