Rafter Length Calculator
Rafter by Pitch & Span
Calculate rafter length from roof pitch and building span
Rafter by Rise & Run
Calculate rafter length from known rise and run distances
Formula
Rafter Length = sqrt(Run^2 + Rise^2) | Rise = Run x (Pitch / 12) | Run = Span / 2
Frequently Asked Questions
How do I calculate rafter length from roof pitch?
Divide the building span by 2 to get the run. Multiply the run by the pitch (rise per foot) to get the total rise. Then use the Pythagorean theorem: Rafter Length = sqrt(Run^2 + Rise^2). Add the overhang tail length separately.
What is the most common roof pitch?
The most common residential roof pitches are 4/12 to 6/12. A 4/12 pitch rises 4 inches for every 12 inches of horizontal run. Steeper pitches (8/12 to 12/12) are used for architectural style and better snow shedding.
You may also need
~
Square Footage Calculator
Free square footage calculator. Calculate area in square feet for rooms, homes, flooring, and landscaping. Supports rectangular, circular, and triangular shapes.
Everyday~
Wood Beam Span Calculator
Calculate the maximum allowable span for wood beams by species, grade, and size. Determine proper beam sizing for floor joists, headers, and ridge beams.
Everyday