Rafter length calculator
Run in feet and pitch as X:12, or rise. Length = run × √(1 + (pitch/12)²).
CopiedAbout this rafter length calculator
Given run and rise (or pitch), estimate the rafter line length along the slope — the hypotenuse of the roof triangle.
Length = sqrt(run² + rise²). Pitch modes convert x/12 into rise for a given run before that step.
Not a birdsmouth cut sheet, hanger schedule, or engineered truss design. Span tables and loads belong to code and a pro.
FAQ
How is length calculated? Length = run × sqrt(1 + (pitch/12)²). Pitch is rise per 12 of run. If you enter rise instead, pitch is (rise/run)×12.
Is this the same as roof pitch? Related. Roof pitch is N:12 from rise and run. This solves the hypotenuse for a given run and pitch.
Does this include overhang or ridge thickness? No. It is the straight-line length for that run and pitch.