Home Calculators Rafter Calculator

Rafter Calculator

Calculate rafter length, roof pitch angle, ridge height, overhang, plumb cut, and bird's mouth seat cut — with a live cross-section diagram.

Roof Dimensions

Enter span, pitch, and overhang to compute all rafter measurements

Full width wall-to-wall

Cross-Section Diagram

Labeled rise, run, span, overhang, and pitch angle

All Measurements

Step-by-Step Calculation

Total Rafter Length

incl. overhang

Pitch Angle

degrees

Ridge Height (Rise)

above wall plate

Plumb Cut

at ridge / peak

Seat Cut (Bird's Mouth)

horizontal cut angle

Slope Factor

rafter per 1 ft run

Common Roof Pitch Reference

Pitch Angle Slope Factor Category Typical Use

Material Estimate