Roof Pitch Calculator

How to Calculate Roof Pitch

All homes and buildings have roofs. They may range from flat to very steep, some may have curves, and others may have multiple peaks and valleys. All of these roofs have one thing in common; however, they all have what is known as a pitch. Roof pitch describes the slope, or angle, of the roof.

Even flat roofs have a pitch, albeit a small one, as that slope is required to prevent rain and snow from gathering.

Knowing a roof’s pitch is essential in determining what type of material should be installed on the roof, the appropriate installation method, and how much roofing material you’ll need. It’s also an important factor in cold climates for calculating snow load.

Roof pitch, or slope, is a measure of vertical rise to horizontal run expressed in inches per foot, which is referred to as rise over run.[1] Meaning that the roof is measured 12″ in from the edge in a horizontal line, then measured from this point straight up to where the roof intersects. A roof that rises 6″ vertically for every 12″ horizontally has a 6″ per foot, or a 6 in 12 pitch.

Thus, the pitch is the ratio of the rise in inches to a 12-inch run and is often expressed using a semicolon, for example, 6:12. Sometimes, the pitch is also expressed in fraction form using a fraction with a slash, such as 6/12.

Method One: Measure From the Roof

One method to find the pitch is to climb on the roof and measure the rise for a 12″ run. You’ll need a level that is 12″ or longer and a tape measure.

On the roof, hold the level perfectly level, and measure the height from the roof to the level 12 inches away from where the level touches the surface; this will be the rise.

For example, if the end of a level is 4″ above the roof at a point 12″ away from where it meets the surface, then the pitch is 4:12.

Method Two: Measure From the Attic

Another method to find the roof pitch is to go into the attic and measure the rise over a 12″ run of the roof rafters, allowing you to find the pitch without going on the roof.

From the attic, hold a level perfectly level and touching a rafter at one end. Measure the distance from the level to the rafter 12 inches away from where the level touches the rafter.[2]

How to Convert Angle in Degrees to Roof Pitch

If you know the roof’s angle in degrees, you can find the roof pitch by converting the angle in degrees to a slope, then finding the rise by multiplying the slope by 12.