Roof pitch is the steepness of your roof, measured by the rise divided by the run. Knowing how to calculate your roof pitch is essential for determining the materials you’ll need for a roofing project as well as understanding the overall look and function of your roof. In this article, we will discuss three methods to calculate the pitch of a roof.

1. Use a Roof Pitch Calculator or App

There are several free roof pitch calculators available online that can quickly compute your roof’s pitch. These tools usually require you to input information such as the width and length of the building, as well as the rise (how much higher one end of the roof is than the other). Many roofing calculator applications are also available for smartphones and tablets, making it easy to calculate your roof pitch on-the-go.

2. Measure with a Level and Tape Measure]

If you prefer to calculate your roof pitch manually or do not have internet access, measuring with a level and tape measure is a simple method. To do this:

a) Set up a ladder near one edge of the roof, climbing high enough to safely reach it.

b) Hold an 18-inch or longer level horizontally parallel with the ground.

c) Measure 12 inches along the level from one end and make a mark.

d) With the level perfectly horizontal, measure up from this mark to the underside of your roofing material. This measurement represents your rise per twelve inches (a standard unit in calculating pitch).

The result expressed as “rise over run” (for example, 4:12 or 6:12) indicates your roof’s pitch.

3. Calculate Using Rafter Lengths

If you have access to blueprints or can measure rafter lengths inside your attic, you can use simple trigonometry to calculate your roof’s pitch. Follow these steps:

a) Obtain or measure your rafter length and half the building’s width (the run).

b) Using a scientific calculator or online trigonometry calculator, find the angle of inclination by performing the arcsine () function on the rise divided by the rafter length.

c) Convert this angle into a slope by finding its tangent (the ratio of rise to run).

d) Express your pitch as “rise over run” (for example, 4:12 or 6:12).

Conclusion

Calculating your roof pitch can be as straightforward as using an online tool or smartphone app or can require manual measurements and simple mathematics. By understanding the methods to determine your roof’s pitch, you’ll be better prepared for any roofing project, whether it’s repair, replacement, or simply understanding how to maintain your home.