Roof Pitch Calculator
Enter the rise and run to get the roof angle, slope, pitch ratio and rafter length.
Result
How to use
- Enter your values in the fields above.
- Press Calculate to see your result instantly.
- Use the Share button to copy a link to your result.
About this calculator
Roof pitch describes how steep a roof is, most commonly expressed in the US as an x:12 ratio — how many inches the roof rises for every 12 inches of horizontal run. From the rise and run, the roof angle is simply the arctangent of rise divided by run, the slope percentage is (rise ÷ run) × 100, and the rafter length for that section of roof comes straight from the Pythagorean theorem: the square root of rise squared plus run squared.
Roofers, carpenters and architects rely on these figures for very practical reasons: pitch determines which roofing materials are suitable (very low-slope roofs need different membrane systems than steep-slope shingle roofs), rafter length drives lumber ordering and framing layout, and steeper pitches shed rain and snow more effectively, which is why building codes in snowy regions often specify a minimum pitch.
Enter the rise and run of your roof section, and the calculator returns the roof angle, slope percentage, the x:12 pitch ratio and the rafter length.
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