Calculate roof pitch, slope, angle, rafter length, area and material needs from rise and run.
Calculate roof pitch, slope, angle, rafter length, area and material needs from rise and run.
Enter values above and click Calculate — results will appear here with the formula explained.
Roof pitch is rise over run, usually expressed as X:12 (e.g., 6:12). Slope is rise/run as decimal, angle is arctangent in degrees. Rafter length is the hypotenuse of rise and run, scaled to your building width.
A 6:12 pitch means 6 inches of rise per 12 inches of run, which is a 26.57° angle and 0.5 slope. Steeper pitches shed snow and water faster but need more material and are harder to walk.
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Roof pitch is rise over run, usually expressed as X:12 (e.g., 6:12). Slope is rise/run as decimal, angle is arctangent in degrees. Rafter length is the hypotenuse of rise and run, scaled to your building width. Formula: Pitch = rise:run; Slope = rise/run; Angle = atan(rise/run) in degrees; Rafter = sqrt(rise²+run²) scaled to span; Area = rafter length × building length
Roof Pitch Calculator: Calculate roof pitch, slope, angle, rafter length, area and material needs from rise and run. Formula: Pitch = rise:run. Example: 6 inches rise, 12 inches run = 6:12 pitch, 0.
Calculate roof pitch, slope, angle, rafter length, area and material needs from rise and run. Formula: Pitch = rise:run; Slope = rise/run; Angle = atan(rise/run) in degrees; Rafter = sqrt(rise²+run²) scaled to span; Area = rafter length × building length
| Field | What to enter |
|---|---|
| Rise (inches) | Vertical rise |
| Run (inches, typically 12) | e.g. 12 |
| Building width / rafter span (feet, optional) | For rafter length and area |
| Waste % (%) | e.g. 10 |
All fields use the exact formulas shown below — results include step-by-step breakdowns you can verify by hand.
Roof pitch is rise over run, usually expressed as X:12 (e.g., 6:12). Slope is rise/run as decimal, angle is arctangent in degrees. Rafter length is the hypotenuse of rise and run, scaled to your building width.
A 6:12 pitch means 6 inches of rise per 12 inches of run, which is a 26.57° angle and 0.5 slope. Steeper pitches shed snow and water faster but need more material and are harder to walk.
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6 inches rise, 12 inches run = 6:12 pitch, 0.5 slope, 26.57°, 13.42-inch rafter per foot of run. For a 24-foot wide building (12-foot run each side), rafter is about 13.42 feet, roof area about 322 sq ft per side.
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