How to Measure Roof Pitch

Before You Climb: Safety First

Two of the four methods below never require leaving the attic or the ground — start there. If you must walk the roof: use a harness tied to a secure anchor, work on a dry day, wear soft-soled shoes, and never work alone. If your roof is above one story or steeper than 8/12, measure from the attic instead and let a professional handle anything on the roof surface.

Method 1: Level and Tape Measure (from the attic)

The safest and most common method — no roof access needed:

1. Find a rafter in your attic and hold a 12-inch level horizontally against its side.
2. Adjust until the bubble is centered — the level is your 12-inch run.
3. Measure vertically from the level's end up (or down) to the rafter, in inches. That is your rise.
4. Pitch = rise/12. A 6-inch measurement is a 6/12 pitch.

Tip: measure at two or three different rafters and use the most common value — attics can hide patched or irregular framing.

Method 2: From the Roof Surface

1. With fall protection in place, place the 12-inch level on the roof plane, pointing up the slope.
2. Center the bubble, then measure from the roof surface to the level's high end at the 12-inch mark.
3. That vertical distance in inches is the rise; pitch = rise/12.

This method reads the finished surface, so thick shingle profiles can add a quarter inch or so of error — close enough for ordering materials, but measure against a rafter tail or batten where possible.

Method 3: Speed Square or Pitch Gauge

Fastest method, zero math: place a speed square (or a printed pitch gauge card) flat on the roof plane or against the rafter, pivot it until the bubble or pointer centers, and read the pitch scale directly. Carpenters carry speed squares anyway, so if one is on site this takes ten seconds.

Method 4: Smartphone Angle App

1. Open any clinometer/angle app and calibrate it on a known-level surface.
2. Lay the phone flat against the roof plane or against a rafter; read the angle in degrees.
3. Convert to pitch: rise = 12 × tan(angle). A 26.57° reading works out to a 6/12 pitch.

Handy for a quick estimate, but phone cases and uneven shingle texture skew readings — treat the result as approximate and confirm with Method 1 if the number matters for ordering.

Which Method Should You Use?

After You Measure

Once you have rise over run, plug it into the Roof Pitch Calculator to get the angle, slope percentage and pitch multiplier — the multiplier converts your footprint into true roof surface area for the Roofing Squares Calculator.