A 6/12 roof
6 in of rise per 12 in of run is an angle of 26.57° and a 50% slope, with a rafter multiplier of 1.118.
Roof Pitch Calculator
Convert rise and run into roof pitch, angle and slope, with rafter length and roof area.
Result
Enter your values and select Calculate to see the result.
Runs in your browser — nothing you enter is sent to a server.
How the Roof Pitch Calculator works
Roof pitch describes how steep a roof is. Enter the rise (vertical) and the run (horizontal) in the same unit. The calculator gives the pitch as rise per 12 units of run (the US convention), the angle in degrees and the slope in percent. Add half the building width to get the rafter length, or the footprint area to get the roof's surface area.
Formulas
Pitch and angle
pitch = rise ÷ run × 12, angle = atan(rise ÷ run)
Rafter multiplier
√(1 + (rise ÷ run)²)
Multiply a horizontal length or area by this to get the sloped length or area.
Examples
Rafter length
For a 6/12 roof on a building 8 m wide, each rafter spans 4 m × 1.118 = 4.47 m, plus the overhang.
Frequently asked questions
What pitch is a 45° roof?
12/12 — the rise equals the run.
What is a low-slope roof?
Roughly anything under 3/12 (14°); it usually needs different roofing materials from steep roofs.
How do I measure pitch?
Hold a level horizontally against a rafter, measure 12 in along it and measure straight up to the roof — that's the rise.
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