How to measure roof pitch

Roof pitch is the vertical rise over 12 inches of horizontal run. Measure the rise over exactly 12 inches and you have the pitch: a 6 inch rise is a 6:12 pitch, which is 26.6 degrees. There are three practical ways to take that measurement, and which one you should use depends on what you can safely reach.

How do you measure roof pitch with a level and tape measure?

Hold a 2 foot level horizontal against the roof surface or a rafter, mark 12 inches along it, and measure straight down to the surface. That vertical distance is the rise, and rise over 12 is the pitch. This is the reference method every other method is checked against. You need a 2 foot level, a tape measure, and somewhere you can safely reach the roof surface or a rafter.

1. Hold the level horizontal against the roof surface or rafter, with one end touching.
2. Mark 12 inches along the level from the end that is touching.
3. Keeping the level truly horizontal, measure straight down from that 12 inch mark to the roof surface.
4. That vertical distance in inches is your rise. Write it as rise over run: a 6 inch drop is a 6:12 pitch.

The run is always 12, so only the rise changes. This is why pitch is quoted as a single number in conversation: a roofer saying "it is an eight" means 8:12.

How do you find roof pitch from inside the attic?

Measuring roof pitch from the attic uses the same level and tape measure against a rafter instead of the roof surface. It gives you the identical number without anyone going up a ladder, which makes it the method worth reaching for first when the attic is accessible.

Hold the level horizontally against the underside of a rafter, mark 12 inches, and measure down to the rafter. Take the reading away from the ridge and away from the eave, where framing members sometimes change angle.

How do you measure roof pitch from the ground with a phone?

Modern phones have the sensors to do this two different ways. Resting the phone directly on a rafter or roof surface reads device tilt and converts it to pitch, which is contact measurement and is as accurate as the level method for practical purposes. Reading from the ground works by lining a guide up with the roof edge through the camera.

Ground readings are the fastest option and the only one that needs no access at all, but they are less precise than contact measurement, because the result depends on how square you are standing to the roof edge. Take a second reading from a different spot if the first one looks wrong.

Pitch Please does both, offline and without an account, and the detail on ground readings is on the Camera Mode page.

How do you convert roof pitch to degrees?

Take the arctangent of rise divided by run. For a 4:12 pitch that is arctan(4 / 12), which is 18.4 degrees. Two anchors worth remembering: a 12:12 roof is exactly 45 degrees, and a 6:12 roof is 26.6 degrees.

The roof pitch chart lists every pitch from 1:12 to 24:12 already converted to degrees, percent slope, and the pitch multiplier used to turn a flat footprint into actual roof area.

What makes a roof pitch reading unreliable?

Two things cause most unreliable roof pitch readings, whichever method you use. Measuring near the ridge or the eave picks up framing that is not representative of the main slope, and measuring a roof with more than one plane gives you the pitch of whichever plane you happened to hit. On a roof with several sections, measure each section separately.

If a number matters financially, take it twice from different points on the same plane and confirm they agree.

Frequently asked questions

How do you calculate roof pitch from rise and run?

Measure the vertical rise over exactly 12 inches of horizontal run. That rise is the pitch: a rise of 6 inches over 12 inches of run is a 6:12 pitch. To express it in degrees, take the arctangent of rise divided by run, so arctan(6/12) is 26.6 degrees.

Can you find roof pitch without getting on the roof?

Yes. Two ways. From inside the attic you can measure the rise and run against a rafter, which is the most accurate method that keeps you off the roof. From outside, a phone app that reads the roof edge from the ground gives you a usable number in a few seconds without a ladder.

What is the most common residential roof pitch?

Most pitched residential roofs in the United States fall between 4:12 and 9:12. A 6:12 pitch, which is 26.6 degrees, is the one people picture when they think of a conventional gable roof.

What tools do you need to measure roof pitch by hand?

A 2 foot level, a tape measure, and a pencil. Mark 12 inches along the level, hold the level horizontal against the rafter or roof surface, and measure straight down from the 12 inch mark to the surface. That vertical distance is your rise.

How accurate is measuring roof pitch with a phone?

Resting the phone directly on a rafter or roof surface reads device tilt and is accurate enough for ordering material and quoting work. Reading from the ground through a camera guide is less precise than contact measurement because it depends on how square you stand to the roof edge, so take a second reading if the first looks off.