Roof Pitch Calculator
Convert between rise/run, degrees, percent and x/12 pitch — with the rafter length multiplier for material estimates.
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Four Ways to Say the Same Slope
American roofing states pitch as rise per 12 of run: a 6/12 roof climbs 6 inches per foot — 26.6°, a 50% grade. Europe talks degrees or percent. The converter takes any one form and returns all four, plus the rafter multiplier (1 ÷ cos θ): at 6/12 every meter of horizontal span needs 1.118 m of rafter/roof surface — the number that scales your shingle and membrane orders.
Practical bands: below 2/12 (9.5°) counts as low-slope and needs membrane, not shingles; 4/12-9/12 is the walkable standard-shingle zone; above 9/12 (37°) means staging and steep-roof rates. Snow country favors 6/12+ so loads shed.
Frequently Asked Questions
How do I measure my existing roof pitch?
From a ladder at the gable: hold a level horizontally touching the roof, measure 12 inches out, then measure straight down to the roof — that drop in inches is your x/12 pitch. Phone inclinometer apps on a rafter also work.
How much more surface does pitch add?
The rafter multiplier applies to area too: a 100 m² footprint at 6/12 carries ~112 m² of roof surface, at 12/12 ~141 m². Order materials by surface, not footprint.
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Roof Pitch Calculator