Roof Pitch Calculator and Chart

Understanding Run and Rise in Roof Pitch

Roof pitch is a way to describe how steep a roof is. It’s based on two measurements: the rise and the run.

The rise is how much the roof goes up vertically. The run is how far it goes across horizontally. These two numbers are used together to express the slope of the roof.

In construction, roof pitch is usually shown as a ratio with the run always set to 12 inches (1 foot). So if a roof rises 4 inches for every 12 inches it runs horizontally, the pitch is called a 4:12 pitch. Common pitches include 3:12 (low slope), 6:12 (standard), and 9:12 or higher (steep).

Here are a few examples:

• 3:12 – the roof rises 3 inches for every 12 inches of run (shallow pitch)
• 6:12 – rises 6 inches per 12 inches of run (medium pitch)
• 12:12 – rises 12 inches per 12 inches of run (steep pitch)

This concept is similar to slope in geometry or the tangent function in trigonometry. Architects and engineers may also express roof pitch in degrees, especially when using CAD software or 3D models. For example, a 6:12 pitch equals approximately 26.57 degrees.

Knowing your roof pitch helps with planning construction, choosing materials, and estimating how water or snow will run off the roof.