Roof Pitch
Free Roof Pitch calculator with clear step-by-step results.
About Roof Pitch
Expresses the same pitch in the three conventions in use - degrees, rise in twelve, and percentage - and derives the slope factor, which is the multiplier that converts plan area into the real surface area you have to cover with material.
Formulas
Pitch
Degrees = arctan(rise / run); rise in 12 = rise / run x 12
Slope factor
Factor = square root of (1 + (rise / run)^2)
Worked example
With the default values below, Roof Pitch returns Pitch in degrees of 30.96. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Riseminimum 1 mm
- 2,400 mm
- Run (horizontal)minimum 1 mm
- 4,000 mm
- Roof plan areaminimum 0.1 m2
- 90 m2
Results
- Pitch in degrees
- 30.96 degrees
- Pitch as rise in 12
- 7.20 in 12
- Pitch as a percentage
- 60.00% %
- Actual sloped roof area
- 104.96 m2
Step by step
- 1Values used
- 2Pitch
- 3Slope factor
- 4Pitch in degrees= 30.96 degrees
- 5Pitch as rise in 12= 7.20 in 12
- 6Pitch as a percentage= 60.00 %
- 7Actual sloped roof area= 104.96 m2
Assumptions and limits
- The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
Why does plan area understate the roof?
Because the roof is the hypotenuse. A 30 degree roof has about 15.5% more surface than its footprint, which is exactly how material orders come up short.
What is the minimum pitch for tiles?
It depends on the product - plain tiles typically need 35 degrees or more, interlocking concrete tiles about 17.5, and profiled metal sheets can go to 5 or lower with sealed laps.