What does "x in 12" pitch mean?

It is the vertical rise for every 12 units of horizontal run. A 4:12 pitch rises 4 units for every 12 along, which equals about 18.4 degrees.

How do I convert a roof angle to pitch?

The tangent of the angle gives the slope, so rise-in-12 equals tan(angle) × 12. Switch to angle mode and the calculator does this conversion for you.

Is anything uploaded?

No — all the maths runs in your browser and nothing is sent to a server.

Roof Pitch Calculator

Convert between rise/run, angle, percent and x-in-12 pitch.

Roof pitch calculator — ratio, degrees and percent

A roof pitch calculator converts between the ways a roof slope is described. Enter the rise and run or a roof angle, and the tool returns the pitch as an x-in-12 ratio, in degrees, and as a percentage slope.

Useful for ordering materials, checking a drawing, or matching an existing roof — and it all runs in your browser with nothing uploaded.