Roof Pitch Calculator
Angle, rafter length, and the area you actually need.
Work out Roof Pitch. Angle, rafter length, and the area you actually need. Shows the working, not just the answer.
Vertical height. Any unit, as long as the run uses the same one.
Horizontal distance. 12 gives the familiar x-in-12 pitch.
Optional — converts to actual roof area.
Roof angle
26.57°
6:12 pitch · slope factor 1.118
Roof area is not footprint area. Multiply by the slope factor, √(1 + (rise/run)²) — a 6:12 roof needs about 12% more material than its footprint suggests, and a 12:12 roof needs 41% more. Ordering to the footprint is a classic and expensive underestimate. Pitch is conventionally written as rise in 12, so 6:12 means six units of rise for every twelve of run. That is 26.6°, not 30° — the ratio and the angle are not the same thing and are often confused. Minimum pitch depends on the covering. Most tiles need at least 4:12 to shed water reliably, while some membranes work almost flat. Going below a material's rated minimum invites leaks whatever else is done right.
How the Roof Pitch Calculator works
Enter rise and run for the roof angle, the pitch ratio, rafter length and the slope factor. Roof area is footprint area times that factor — ordering to the footprint is a classic and expensive underestimate.
Also known as: roof angle calculator · rafter length calculator · roof pitch to degrees · roof area from footprint
Frequently asked questions
How do I calculate roof pitch?
Rise divided by run, conventionally expressed as rise in 12. A roof rising 6 units over 12 of run is a 6:12 pitch, which is 26.6°.
Is 6:12 the same as 30 degrees?
No — 6:12 is 26.57°. The ratio and the angle are different things and confusing them is common. A 12:12 pitch is exactly 45°, which is the one case where the numbers feel intuitive.
How do I find the actual roof area?
Multiply footprint area by the slope factor, √(1 + (rise/run)²). A 6:12 roof needs about 12% more material than its footprint; a 12:12 needs 41% more.
What is the minimum pitch for tiles?
It depends on the covering, and manufacturers publish a rated minimum. Most tiles need at least 4:12 to shed water reliably; some membranes work almost flat. Going below the rating invites leaks whatever else is done correctly.
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