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Roof Pitch Calculator

Calculate roof pitch angle, slope percentage, and rafter length.

RunRise14.0°
Angle
14.04°
Pitch ratio
3.00:12
Slope %
25.0%
Rafter length
12.369 m
Roof type: Low pitch

Roof pitch and rafter length calculator

Calculate pitch angle, slope percentage, x:12 ratio, and rafter length from any two known values. A visual diagram shows the roof geometry.

Frequently asked questions

What is roof pitch?
Roof pitch is the slope of a roof, typically expressed as a ratio of rise to run (e.g., 4:12 means 4 inches of rise per 12 inches of horizontal run) or as an angle in degrees.
What is a standard roof pitch?
A 4:12 to 6:12 pitch (18–27°) is the most common residential roof pitch. Low pitch roofs are 2:12 or less, conventional is 4:12 to 9:12, and steep roofs are 9:12 and above.
How is rafter length calculated?
Rafter length = √(run² + rise²) = run / cos(angle). This gives the slant length of the rafter from the wall plate to the ridge.

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