Calculate rafter length from rise, run and building span — includes overhang and birdsmouth options.
Calculate rafter length from rise, run and building span — includes overhang and birdsmouth options.
Enter values above and click Calculate — results will appear here with the formula explained.
Rafter length is the hypotenuse scaled to your building's half-span, plus overhang. For a 24-foot span, half is 12 feet (144 inches) of run.
Add overhang after scaling — it extends beyond the wall, not part of the triangle.
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Rafter length is the hypotenuse scaled to your building's half-span, plus overhang. For a 24-foot span, half is 12 feet (144 inches) of run. Formula: Rafter = sqrt(rise²+run²) × (span/2 / run) + overhang
Rafter Length Calculator: Calculate rafter length from rise, run and building span — includes overhang and birdsmouth options. Formula: Rafter = sqrt(rise²+run²) × (span/2 / run) + overhang. Example: 6:12 pitch, 24-foot span, 12-inch overhang: rafter ≈ 13.
Calculate rafter length from rise, run and building span — includes overhang and birdsmouth options. Formula: Rafter = sqrt(rise²+run²) × (span/2 / run) + overhang
| Field | What to enter |
|---|---|
| Rise (inches) | e.g. 6 |
| Run (inches) | e.g. 12 |
| Building span (feet) | e.g. 24 |
| Overhang (inches, optional) | e.g. 12 |
All fields use the exact formulas shown below — results include step-by-step breakdowns you can verify by hand.
Rafter length is the hypotenuse scaled to your building's half-span, plus overhang. For a 24-foot span, half is 12 feet (144 inches) of run.
Add overhang after scaling — it extends beyond the wall, not part of the triangle.
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AdSense ready — add NEXT_PUBLIC_GOOGLE_ADSENSE_PUBLISHER_ID
6:12 pitch, 24-foot span, 12-inch overhang: rafter ≈ 13.42 feet + 1 foot = 14.42 feet.
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