How to Measure Roof Pitch (Without Getting on the Roof)

Hold a level against a rafter, mark 12 in along it, and measure straight up to the rafter. That number is your pitch: 6 in means a 6/12 roof.

Updated October 7, 2026

What Pitch Means

Roof pitch is written as rise/12: how many inches the roof climbs for every 12 in it runs level. A 4/12 roof is fairly shallow (18.4°); a 12/12 roof climbs at 45°.

Three Ways to Measure It

From the attic (safest). Hold a 2 ft level horizontally with one end touching the underside of a rafter. Mark the level at 12 in from that end. Measure straight up from the mark to the rafter. That measurement in inches is the rise: 6 in means 6/12.

From a ladder at the gable end. Hold the level against the bottom edge of the rake trim, level it, and measure up from the 12 in mark the same way. Keep three points of contact on the ladder.

With your phone. Many level and measuring apps read angles. Lay the phone on a rafter or along the rake trim, read the degrees, and enter the angle in the roof pitch calculator, which converts it to x/12.

If your measurement doesn’t come out to a whole number, round to the nearest half inch; roof framing often isn’t perfect.

Reading the Result

The shingle limits come from the Asphalt Roofing Manufacturers Association: never below 2/12, and from 2/12 to under 4/12 only with two layers of underlayment or a self-adhering membrane.

Using Pitch to Size a Roof

Multiply your house’s footprint (with overhangs) by the slope factor for your pitch to get the roof’s real area. The roofing calculator does this and converts it to squares and bundles.