What this tool does
Choose the input you already know: rise and run, pitch per 12, angle or percentage slope. The calculator converts that value into the other common roof-pitch formats and displays a simple pitch diagram.
Formula
slope = rise ÷ run; angle = arctan(slope); rafter multiplier = √(1 + slope²)
Examples
6 in rise · 12 in run
6:12 · 26.57° · 50% · multiplier 1.118
Frequently asked questions
Does this calculate rafter length?
It provides the multiplier. Multiply horizontal run by the rafter multiplier for the corresponding sloped length before allowances.
Is the pitch classification a code check?
No. Confirm drainage, material and structural requirements for the project location.