Roof Rafter Calculator – Calculate Rafter Length & Framing Lumber
Calculating roof rafter length manually requires complex right triangle math based on roof span and pitch. Many DIY builders mismeasure rafters and waste expensive framing lumber. This calculator computes the diagonal rafter run and estimates total rafter quantity for gable and shed roof construction for garages, sheds and small residential outbuildings.
Tool Features
- Calculates diagonal rafter length from span and roof pitch ratio
- Estimates total number of rafters needed for full roof width
- Three common roof pitch presets for shed & gable builds
- Supports 16in / 24in standard rafter on-center spacing
- Free shed & garage roof framing planning tool
Common Usage Scenarios
- Storage shed gable roof framing material planning
- Detached garage roof rafter lumber estimates
- Small backyard outbuilding roof design layout
- DIY roof framing cut list preparation
Frequently Asked Questions
Q: What roof pitch works best for shingles?
A: Asphalt shingles require minimum 4/12 roof pitch for proper rain runoff drainage.
Q: 16 vs 24 inch rafter spacing difference?
A: 16in spacing creates stiffer roof sheathing; 24in reduces lumber cost for light load sheds.