How to measure roof pitch

Here, roof pitch means vertical rise per 12 inches of horizontal run. A rise of 6 inches over that run is 6:12, also written 6/12, or 26.6 degrees. A level and tape or a phone contact reading can check a safely accessible roof surface or attic rafter. Camera Mode provides photo documentation with a device reading; it does not calculate roof geometry from the image.

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

Hold a 2 foot level horizontal against a safely accessible roof surface or rafter. Mark 12 inches along it, then measure the vertical distance to the surface. That rise over 12 inches of horizontal run is the roofing pitch convention. You need a level and tape measure, and must follow the access and safety requirements for the site.

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?

In Direct Mode, a phone resting along a safely accessible rafter or roof surface reads device inclination and converts it to pitch. Check calibration and placement. This is a field reference method, with no claimed equivalence to a professional level.

Camera Mode displays the phone's sensor reading beside a fixed guide in the live camera view. Aligning the guide with a visible sloping roof profile can help document the scene, but the app does not calculate roof geometry from the image. Perspective and phone orientation can change the result. A stable indicator means the sensor reading has settled; it does not confirm the roof angle.

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 horizontal run. For 4:12, arctan(4 / 12) is 18.4 degrees; 6:12 is 26.6 degrees and 12:12 is 45 degrees. The roof pitch chart lists 1:12 to 24:12 and the factor for converting horizontal projected roof-plane area to sloped surface area.

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?

Possible sources of error include uneven contact, calibration, phone orientation, perspective in Camera Mode, and framing that differs from the main roof plane. Measure each roof section separately. Do not use a horizontal eave or gutter as a substitute for a sloping roof profile.

If a measurement affects material orders, a final estimate, engineering, code, or safety, verify it with the appropriate instruments and requirements. Agreement between two phone readings alone does not establish accuracy.

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?

An accessible attic rafter can provide a contact measurement using a level and tape without climbing onto the roof. Follow site access and safety requirements. Camera Mode can document the scene from the ground with a fixed guide and phone-inclination reading, but it does not calculate roof geometry from the image.

How do I identify the pitch of my roof?

There is no single pitch that describes every residential roof. Measure each roof plane rather than assuming a typical value. For reference, 4:12 is 18.4 degrees, 6:12 is 26.6 degrees, and 8:12 is 33.7 degrees.

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?

Phone readings depend on calibration, placement, contact, and orientation. Camera alignment adds perspective limitations because the app reads device inclination, not roof geometry from the image. Use Pitch Please as field reference and independently verify readings used for material orders, final estimates, code, engineering, or safety decisions.