Roof Pitch Calculator
Pitch describes geometry, not structural adequacy. Measure rise and horizontal run in the same unit, or enter roof planes directly for more complex roofs.
How to use this calculator
Enter rise and horizontal run in the same unit.
Optionally enter horizontal projection or individual roof-plane dimensions.
Review angle, multiplier, sloped area, squares, and the optional bundle estimate.
Formula
Angle = atan(rise ÷ run). Slope multiplier = √(rise² + run²) ÷ run. Sloped area = horizontal projected area × multiplier.
Worked example
A 6-in-12 roof has multiplier √(6² + 12²) ÷ 12 ≈ 1.118. A 1,000 ft² projection therefore has about 1,118 ft² of sloped area.
Assumptions and limits
- Run is horizontal, not measured along the rafter.
- Roof area excludes overhangs unless included in the entered projection.
- Default extra material is 10%; default bundle rate is 3 per square and is editable.
Sources
- National Institute of Standards and Technology: Circumference, Area and VolumeArea and volume formulas for common geometric shapes. Reviewed 2026-08-14.
- National Institute of Standards and Technology: Unit ConversionExact unit conversion and final-result rounding guidance. Reviewed 2026-08-14.
- GAF: Pro Field Guide for Steep-Slope RoofsRoof-plane, slope, and steep-slope roofing terminology. Reviewed 2026-08-14.
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Verification
How this calculator is checked
Trust comes from reproducible evidence, not model confidence. You can inspect the formula, assumptions, worked example, and cited sources on this page.
- Versioned calculationFormula logic is kept separate from the interface and covered by automated registry and behavior checks.
- Cited evidenceSources linked for independent checking: 3.
- Transparent AI useAI may assist drafting or adversarial review. Agreement between models is not proof, and no human expert review is claimed unless a named reviewer is shown.
Frequently asked questions
Is roof pitch enough to size rafters?
No. Structural member sizing requires loads, spans, species or product properties, connections, and applicable building rules.
Can I use metric and US customary units in the Roof Pitch Calculator?
Yes. Unit changes convert the same canonical measurement; they do not reinterpret or round your original value.
When does the calculator round?
The calculation keeps full precision internally and rounds only the displayed result. Whole packages are rounded up at the final step.
Last updated 2026-08-25 · 1.0.0 · 1.0.0 · Published by YunFanLabs