How long do my rafters need to be?
For a simple gable roof. Enter the building width wall to wall, the pitch, and the overhang.
Rafter length
14 ft 6 in
How to measure
Measure the building width from the outside of one wall to the outside of the other. Choose the pitch and how far the overhang should extend past the wall.
Tips from the field
- Measured along the top edge of the rafter. Subtract half the ridge board thickness from each rafter.
- Check local code for rafter size and spacing based on span and roof load.
What you'll need
Common questions
How do I find rafter length?
Divide the building width in half for the run, multiply by the pitch factor, then add the overhang length along the slope.
Do I subtract for the ridge board?
Yes. Subtract half the ridge board's thickness from each rafter, measured level.
What size rafters do I need?
It depends on span, spacing, and roof load. Check the span tables in your local building code.
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Printed from housecalcs.com/tools/rafter-length-calculator