Determine the pitch of a rafter

Find the pitch of any bastard pitch rafter with incredible ease and accuracy with the free Builder Fraction Calculator app.

Learn how to determine the roof pitch equivalent for any known rise and known run with the workshop below. This way you can use a framing square to get more precise cuts on rafters and other framing components.

Install now:

iOS download

Android download

Open app

Builder Fraction Calculator
Click on menu in the top left.

Select Diagonal

Menu for pitch calculator
Click on diagonal at the top.

The Rise

Rise
Enter the rise and click equals.

The Run

Run
Enter the run and click equals.

Results

Rafter pitch
The rafter pitch is 4 / 12.