Property Improve · Roofing
Roof Pitch Calculator
Convert pitch between rise:12, degrees, and slope % — and get the surface-area multiplier and walkability category.
Enter your pitch
How to measure pitch yourself
From the attic: hold a level horizontally against a rafter. Measure 12 inches along the level, then measure straight up to the underside of the rafter. That vertical measurement is your rise per 12.
Phone app: any "level" app on a smartphone laid flat against the roof surface reads the angle in degrees — switch this calculator to degrees mode.
From a photo: harder. A drone shot from a known angle is the only reliable photo method; ground photos distort foreshortening.
More about this estimate
Why pitch matters for cost
Pitch drives two cost lines: material (more surface = more shingle) and labor (steeper = slower install + safety setup). The material side is linear — a 12:12 roof has 1.41× the material of a flat one with the same footprint. Labor scales nonlinearly — a 6:12 crew works at full speed; a 12:12 crew uses roof jacks and harnesses, slowing 30–50%; an 18:12 crew needs scaffolding.
Common roof pitches and what they mean
- 2:12 to 4:12 (low slope) — usually requires modified bitumen, TPO, or specialty underlayment. Standard asphalt shingles are not rated for slopes under 2:12; under 4:12 they need ice-and-water shield over the entire surface.
- 4:12 to 9:12 (conventional) — the sweet spot for asphalt shingles. Walkable, cheap to install, no special equipment.
- 10:12 to 12:12 (steep) — fall protection mandatory, labor +30–50%. Common on Victorian and steep-pitched contemporary homes.
- 13:12+ (very steep / cathedral) — scaffolding territory. Material has to be hand-walked up; productivity drops significantly.
How to measure pitch yourself
- Attic method: hold a level horizontally against a rafter on the underside. Measure 12 inches along the level, then measure straight up to the rafter. That vertical distance is your rise per 12.
- Phone level: any "level" or "angle" app on a smartphone, laid flat against the roof surface or a rafter, reads the angle in degrees. Switch this calculator to degrees mode.
- Don't measure pitch from a ground photo — perspective distortion makes any visual estimate unreliable. Drone shots from a known altitude work; eyeball estimates from the sidewalk do not.
The X:12 convention explained
Roofers always express pitch as rise per 12 inches of horizontal run. Why 12? Because most roofing measurements (shingle exposure, drip edge, ridge cap) are inch-based and the framing square is graduated to 12. A "6:12 pitch" means: for every 12 inches you move horizontally along the roof, the surface rises 6 inches. The ratio fully describes the slope; degrees and percent slope are derived from it.
About this calculator
Reviewed by Eurocraft, a Texas-licensed general contractor. See methodology for the multiplier tables.