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
Related calculators
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 · formula-v1 · content-2026-08-14 · Trusty Calculator Editorial Team