The three ways roofers say pitch
The same roof is described three ways: pitch per 12 (6/12), angle in degrees (26.6°), and percent grade (50%). Enter any rise and run and the calculator converts between all of them, plus the area multiplier that turns a flat footprint into actual roof surface for ordering.
Why the multiplier matters for ordering
The multiplier is how much bigger the sloped roof is than the footprint. A 6/12 roof multiplies by 1.118, a 12/12 by 1.414 — forget it and you order three squares short on a simple gable. Every material calculator on this site that takes a pitch asks for the multiplier this page produces.
Sources and standards
Where these figures come from
Every formula on this page is implemented from the published reference material below. Where a value depends on a regional code, the calculator lets you override it rather than assuming one jurisdiction.
- National Roofing Contractors Association — installation standards for steep- and low-slope roof systems.
- FEMA Building Science — wind and snow load guidance for residential roofs.
- American Society of Civil Engineers — ASCE 7, the source of the ground snow load maps used in roof design.
Figures, formulas and reference tables last verified: 19 September 2026.