Slope is defined as a roof’s vertical rise (in inches) per foot of horizontal run (Slope vs. Pitch, below). For example, a 6:12, or “six-in-twelve,” roof rises 6 in. for every ft. of run. 

Don’t confuse “slope” and “pitch.” Slope is inch of rise per foot of run. Pitch is the ratio of rise to span.
Don’t confuse “slope” and “pitch.” Slope is inch of rise per foot of run. Pitch is the ratio of rise to span.

Slope = Rise/Run

Pitch is different from slope; it’s the ratio of rise to span. For example, a roof sloped at 6:12 has a pitch of 1/4.

Pitch = Rise/Span

Note: Many building professionals use the Construction Master to solve roof framing calculations, and this tool uses "Pitch" when that button should read "Slope."

For more on framing roofs and installing roofing, visit the JLC Field Guide.