Roof Pitch Calculator
Convert a roof rise and run into pitch, angle, rafter length and slope percentage.
Recent
Formula
How the calculation works
The pitch is the rise over the run, shown as the familiar X-in-12 figure builders use.
The same ratio gives the angle in degrees and the slope as a percentage, so the roof can be described in any of the three ways.
The rafter length comes from the two sides, so a steeper pitch needs a longer rafter for the same span.
Common mistakes
- Mixing rise and run units, so a pitch that looks like 6-in-12 is really something else.
- Forgetting that very low pitches need different roofing materials to shed water reliably.
When to use it
- Use it to check a roof's pitch and rafter length when planning or quoting.
- It is not a structural check; load and span need an engineer's sign-off.
Worked example
A rise of 6 over a run of 12 is a 6/12 pitch, a 26.57 degree angle, a 13.416 ft rafter and a 50% slope.
Common questions
What does 6/12 pitch mean?
The roof rises 6 inches for every 12 inches of horizontal run.
Which pitch is common in Bangladesh?
Between 4/12 and 9/12 is common; flatter roofs risk water pooling in heavy rain.
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