About this calculator

Roof pitch is the slope of a roof. In the US it's quoted as 'rise over 12' (e.g. 6/12). Elsewhere it's degrees or a ratio. Enter any one and the rafter length is derived from the half-span.

Formula: Angle = arctan(rise / run); Rafter = √(rise² + run²)

Frequently asked questions

What does the Roof Pitch Calculator do?

Convert roof pitch between rise/run, degrees and ratio. Get rafter length from span. Roof pitch is the slope of a roof. In the US it's quoted as 'rise over 12' (e.g. 6/12). Elsewhere it's degrees or a ratio. Enter any one and the rafter length is derived from the half-span.

Is the Roof Pitch Calculator free to use?

Yes. Every calculator on Calcora is free, works in your browser without sign-up, and can be embedded on your own website.

How accurate is the Roof Pitch Calculator?

Results are calculated in real time using the formula Angle = arctan(rise / run); Rafter = √(rise² + run²). Treat the output as a well-informed estimate — always cross-check with local regulations, product datasheets, or a qualified construction & building professional before committing to a purchase or a job.

What inputs does the Roof Pitch Calculator need?

Enter values for: Rise, Run (half-span). Sensible defaults are pre-filled where possible so you can start with a single change.

Can I embed the Roof Pitch Calculator on my own website?

Yes — copy the iframe snippet at the bottom of this page, or use the Embed Generator to customise the size. The embedded version stays in sync with the live calculator on Calcora.