How to Calculate Roof Pitch: Rise, Run & Ratios

Whether you are framing a new addition or planning a roof replacement, knowing your roof's steepness is the first step. If you are wondering how to calculate roof pitch, the process comes down to two simple measurements: the vertical rise and the horizontal run.

Understanding Rise and Run

In the US roofing industry, pitch is expressed as a ratio of inches over a standard 12-inch run. To calculate pitch of roof structures, you need to measure how many inches the roof rises vertically for every 12 inches it extends horizontally toward the peak. For example, if your roof rises 6 inches over a 12-inch horizontal span, you have a 6/12 roof pitch.

The Fastest Way to Find Your Pitch

While you can do the math manually using a tape measure and a level in your attic, professionals save time by using an online roof pitch calculator. Once you have your basic rise and run measurements—even if your run isn't exactly 12 inches—you can simply plug them into our Roof Pitch Calculator. The tool will automatically reduce your ratio to the standard X/12 format, saving you time and preventing costly mathematical errors.