Rafter Length

Formula and source

Rafter length L = sqrt(run² + rise²) plus tail and ridge plumb cuts. Birdsmouth depth limited to 1/3 rafter depth per IRC 2021 §R802.5.

IRC 2021 (International Residential Code). §R802.5.

Audience

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Related tools

• Roof Pitch
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Posture

Rough Logic answers the math question the working professional asks on the job. The site is a calm, fast, ad-free, account-free, ever-free reference. It does not interpret code. It does not replace the licensed professional. It does not store your inputs. The Authority Having Jurisdiction governs all installations and inspections.