Rafter Length Calculator

Calculate horizontal run, roof rise, rafter length, and approximate board length for a simple symmetrical roof.

Building span (ft)

Roof pitch (rise per 12)

Ridge board thickness (in)

Horizontal overhang (in)

—Rafter run

—Roof rise

—Wall-to-ridge length

—With overhang

—Simple common-rafter geometry; cut details and structural sizing are not included.

Use project drawings and local requirements for actual framing. This calculator does not determine member size, load capacity, birdsmouth cuts, connections, or code compliance.

How to use this Rafter Length Calculator

Estimate common rafter length from roof span, pitch, ridge thickness, and overhang. Enter your values above and the result is calculated directly in your browser. No account is required.

Fast answer, clear inputs

This tool is built around one job: give the answer quickly without forcing a signup or hiding the result. Related tools are linked nearby when the next calculation or conversion is useful.