How to Measure Roof Pitch

Updated October 29, 2026 · Foster Apps

Hold a level horizontally against the roof with one end touching the surface. Measure 12 inches along the level, then measure straight down from that point to the roof. That distance in inches is your pitch: 6 inches means a 6/12 roof.

What you're measuring

Roof pitch is how many inches the roof rises for every 12 inches it runs horizontally. A 6/12 roof climbs 6 inches over each foot. Every method below finds those two numbers, a rise and a run, then scales them to a run of 12.

1. Level and tape measure, on the roof

1. Mark 12 inches from one end of a 2-foot (or longer) level.
2. Hold that end against the roof surface, and hold the level out horizontally, checking the bubble.
3. At the 12-inch mark, measure straight down (vertically) from the bottom of the level to the roof.
4. That number is the rise per 12. Measure in a couple of spots and away from bumps in the shingles.

With a 24-inch level, you can measure at the 24-inch mark instead and divide by 2. A longer distance averages out small bumps.

2. From the attic, on a rafter

This is the safest method, and the rafter isn't covered by shingles. Hold the level against the underside of a rafter, keep it level, and measure straight up from the 12-inch mark to the rafter. The rafter has the same pitch as the roof above it.

3. With a speed square

1. Put the speed square's pivot point (the corner marked "pivot") against the bottom edge of a rafter or a fascia board.
2. Rotate the square until its edge is level. A small level on top helps.
3. Read the common scale where the rafter edge crosses it. That number is the rise per 12.

4. From the ground, at a gable end

On a simple gable roof, you can measure the triangle on the end wall:

1. Run: half the width of the house, from the outside of the wall to directly under the ridge.
2. Rise: from the top of the wall (where the roof starts) to the ridge. Count siding courses and multiply by their exposure if you can't reach.
3. Pitch = rise ÷ run × 12. A 6-foot rise over a 14-foot run is 6 ÷ 14 × 12 = 5.1, about a 5/12.

5. With your phone

A phone's motion sensor can read an angle. Lay the phone flat on the roof surface or a rafter, screen up, and read the angle. Then convert it with the roof pitch to degrees chart. The Foster Tools roof pitch calculator does this directly on a phone: tap Measure, lay the phone down, and it shows the pitch.

• Calibrate on a known flat surface first, and take the reading on bare wood or flat shingles, not on a ridge cap or a lump.
• A phone case with a camera bump tilts the phone. Take it off, or calibrate with it on.

6. From the plans or the permit

House plans and roof truss drawings usually mark the pitch with a small triangle symbol, such as "6 over 12". Truss companies stamp the pitch on the truss drawings too.

Safety

• Measure from the attic or the ground if you can. Most falls happen near the edge and on the ladder.
• Don't go on a roof that's wet, frosty or steeper than about 8/12 without fall protection.
• Keep the ladder 3 feet above the edge and tied off.

Once you have the pitch

To work out the roof area and how many shingle squares to order, use the roof pitch multiplier.