Home Articles

Roof Pitch Angles: How to Calculate Your Roof Pitch

Written by Chris Gennone

Published on April 6, 2021


Roof Pitch Angles: How to Calculate Your Roof Pitch

With our help, you'll be able to calculate and estimate your roof pitch angles easily. Learn more today!

To provide you with the most accurate and up-to-date information, we consult a number of sources when producing each article, including licensed contractors and industry experts.

Read about our editorial process here. Want to use our cost data? Click here.

Understanding your new roof's pitch and slope is incredibly important. This helps you understand how excess water, snow, or debris falls off the roof, which also helps guide you to the right type of shingles or roofing materials you need. We're here to teach you how to easily calculate and estimate your roof pitch angles manually.

Key terms

Before calculating the pitch of your roof, let’s go over some basic key terms and measurements so everything is on point.

Rise and run

Rise is the vertical measurement of the distance from one point of your roof to the highest point of the roof. If you look at a right-degree angle or a right triangle, you’ll see the rise as the vertical component and the run as the horizontal component.

Run is the horizontal measurement of how far out your roof extends, typically the distance from the peak of your roof to the exterior wall.


Roof slope is often perceived as the same thing as pitch and it's important to understand the subtle difference. Slope is the incline of the roof, and it is represented in a ratio measured in inches of the vertical rise per foot of the horizontal run. For example, a roof with a 4-inch rise for every 12 inches of run, this ratio would look like 4:12. The ratio always represents inches per foot.


Pitch is the incline of the roof and is instead represented in a fraction dividing the rise by the span, which is the distance between outside walls. For example, a roof with a rise of 4 feet and a span of 24 feet would represent a ? pitch of the roof.

Roof Angles

Depending on what type of roof you have, you'll have a different slope ratio or pitch fraction. Let's take a look at some of the main roof types and determine what category your roof falls into.

Flat roofs or low pitch/low slope roofs will typically have a lower ratio and fraction, usually from 1/12-2/12.

More common gable roofs will have a higher slope ratio or fraction from 4/12 to 9/12.

And roofs with a steeper pitch/steep slope, you could see a fraction up to 18/12 or higher.

How to manually calculate your roof pitch

How to calculate your roof pitch on the roof

If you'd like to calculate your pitched roof manually for an exact measurement and aren't afraid of heights, whip out the tape measure and spirit level, and carefully climb the ladder to access your roof. Whether you have an asphalt shingle roof, rubber membrane, or metal roof, always make sure it's safe to stand on your roof first.

Once you're safely on your roof, measure 1-foot up from the base, which will give you the run. Then place the spirit level at the 1-foot marker, and once it is even, measure from the bottom of the level to the top of your roof. This will give you the rise.

For example, if your rise is 6 inches, then your roof pitch will be 6/12. For every 12 inches of horizontal run, the roof rises 6 inches.

How to calculate your roof pitch from onside

An easier way to calculate your roof pitch without going on the roof is to measure the rafter length or truss system in your attic. Place your level under the bottom of the rafter, and after the bubble is in the center, mark it at 12 inches. Then measure vertically from the level to the roof rafter. This measurement will tell you the number of inches your roof rises in 12 inches of run.

Measure your roof’s pitch today

Now that you’re equipped with the proper tools to calculate your roof’s pitch, it’s time to get measuring! Determine the pitch of your roof with our handy guide and find a local roofer to handle your next roofing project today.

Find the best local roofers near you

Written by

Chris Gennone Author

Chris Gennone is a content specialist and video producer at Fixr.com. He has 5 years of experience writing and editing for a variety of web and print publications, currently specializing in home improvement projects such as roofing, remodeling, and repairs. When Chris isn’t writing or in front of the camera, he’s either playing with his band or tracking down the best sandwich shops.