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Roof pitch calculator
Convert rise and run into pitch, angle, slope and diagonal length.
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- Calculated on your device
02 / Your results
| Measurement | Result |
|---|---|
| Vertical rise | 6 in |
| Horizontal run | 12 in |
| Sloped length | 13.416 in |
| Roof area multiplier | 1.118× |
Multiply the horizontal plan area by 1.118 for the sloped area at this pitch. This excludes overhangs and material waste.
How the calculation works
Pitch per 12 scales rise to a 12-unit run. Angle uses arctangent, while the diagonal uses the Pythagorean theorem. This is a geometry estimate, not structural design advice.
Try an example
A rise of 6 over a run of 12 gives a 6:12 pitch, a 26.57° angle and a 50% slope.
How to use this calculator
- Choose inches or centimetres. Use a known vertical rise and horizontal run from the same right triangle, such as dimensions on your plans.
- Enter the rise and run. Run is the horizontal distance for the slope being measured; for one side of a simple gable roof, use eave-to-ridge distance.
- Select Calculate pitch to see pitch per 12, angle, slope percentage, sloped length and the area multiplier.
Common questions
What does a 6:12 roof pitch mean?
A 6:12 pitch rises 6 units for every 12 units of horizontal run. That is a 50% slope and approximately a 26.57° angle from horizontal. The ratio is the same in inches or centimetres.
Is run the full roof span or the sloped length?
Run is horizontal. For one slope of a symmetric gable roof, it is half the horizontal span between eaves. Entering the sloped length or the full span as the run gives the wrong pitch.
Can I use the result to cut rafters or order materials?
The result describes only the entered right triangle. It excludes overhangs, joints, cuts, roof openings and material waste. It does not determine structural capacity or a rafter-cutting plan.