Roof Pitch Calculator
Use this roof pitch calculator to turn rise and run into pitch (X/12), angle, slope percent, and a rafter length multiplier. Enter rise and run in the same unit, or type an angle to read the pitch.
Math runs in your browser. Nothing is uploaded.
Pitch (X/12)
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Angle (°)
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Slope %
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Length multiplier
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Pitch X/12 = (rise/run)×12. Angle = atan(rise/run)×180/π. Multiplier = √(1+(rise/run)²).
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How it works
- What is roof pitch?
- Roof pitch is how steep a roof is, written as rise over a 12-inch run. A 6/12 pitch rises 6 inches for every 12 inches of horizontal run.
- How do I calculate roof pitch from rise and run?
- Pitch (X/12) = rise / run × 12, with rise and run in the same unit. A rise of 6 over a run of 12 is 6/12, which is a 26.57° angle and a 50% slope.
- How do I convert roof pitch to degrees?
- Angle = arctan(rise / run). Common values: 4/12 is 18.43°, 6/12 is 26.57°, 8/12 is 33.69°, and 12/12 is 45°.
- What is the rafter length multiplier?
- The multiplier is √(1 + (rise / run)²). For 6/12 it is about 1.118, so a rafter over a 10 ft run is about 11.18 ft before overhang and ridge adjustments.
- Is any data uploaded?
- No. These calculators and QR codes run in your browser.