Roof Pitch Calculator
Roof pitch in the US is written as rise per 12 inches of run (a '6-in-12' roof rises 6 inches per foot). Enter your rise and the footprint dimensions — you get the pitch, the angle in degrees, the slope multiplier estimators use, and the actual roof surface area that material orders are based on.
The math behind pitch
The slope multiplier converts a flat footprint into the true sloped area. A 6-in-12 roof has a multiplier of about 1.118 — you need 11.8% more material than the footprint suggests.
Common pitches: 3-in-12 is a shallow roof (multiplier 1.031), 6-in-12 is standard (1.118), 9-in-12 is steep (1.250), and 12-in-12 is a 45° slope (1.414).
This gives the area of one rectangular roof face. For gable roofs, apply the multiplier to the full footprint; for hip roofs, the multiplier for the same pitch is slightly lower.
Frequently asked questions
What is the most common roof pitch?
Residential roofs in the US commonly sit between 4-in-12 and 9-in-12. Conventional shingles typically need at least 2-in-12 with underlayment.
How do I measure rise without climbing the roof?
From the attic: hold a level 12 inches horizontally from the rafter, measure the vertical drop to the rafter — that's your rise per 12.
Why do I need the multiplier?
Material must cover the sloped surface, not the footprint. Ordering by footprint under-orders shingles by exactly the multiplier ratio.
Related tools
- Geometry: standard right-triangle relations (arctan, Pythagorean multiplier). Pitch conventions: US roofing industry practice.
Last updated: 2026-09-08