Rafter Cut & Roof Framing

A framing calculator for cutting rafters — enter span and pitch to get rafter length, plumb and seat cut angles, and a scaled drawing you can mark from, in seconds.

Whether you're framing a shed roof, a garage, or a porch addition, this app removes the trigonometry from laying out common, hip and valley rafters.

Key Features

- Common, hip and valley: Switch rafter type with one tap. Hip and valley use the 45-degree diagonal run automatically.
- Pitch in any unit: Enter x/12, degrees or percent — switching units converts the value instead of resetting it.
- Plumb and seat cut angles: Get both cut angles for the rafter type you selected, matching your framing square.
- Overhang and tail: Enter a horizontal overhang to get the tail length along the slope and the full cut length.
- Scaled cut diagram: See run, rise, rafter length and cut angles drawn to scale as you type.
- Rafter count: Enter building length and 12, 16 or 24 inch spacing to get the number of rafters.
- Feet-inch-fraction: Lengths round to 1/32 inch. Type 3 1/2 or 3.5, and comma decimals work too.
- Project history: Save up to 20 jobs locally and reload one for a new roof.
- Works offline: Every calculation, diagram and save runs on the device. No account, no network.

Recommended For

- Carpenters and framers cutting rafters on site
- DIY builders framing a shed, garage or porch roof
- Anyone checking rafter numbers against a framing square before cutting

This app is a layout aid, not a structural design. It does not judge loads, spans, birdsmouth depth limits or local building code. Confirm those with your plans and inspector, and always cut one rafter first and test-fit it before cutting the rest.