Jack rafter spacing calculator
Roof pitch and rafter spacing to how much shorter each jack rafter gets than the one before it, the line a framer checks on site.
What you enter
- Pitch rise (in / 12)
- Pitch run (in)
- Rafter spacing (O.C.) (in)
Main results
- Slope factor
- How much shorter each jack rafter is than the one before it (in)
What it follows
Plain geometry: the slope factor times your rafter spacing; no building-code table is looked up.
Every result is marked REVIEW REQUIRED. Illustrative project-planning values only; jurisdiction, species, grade, loads, wet service and current adopted tables require review. Do not use a result directly for permit, purchase, or field use.
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The calculator opens inside the designer, after you sign in.
Accounts are issued by the DeckAndShed team. There is no self-service sign-up.