How to Measure Roof Pitch (3 Easy Methods)
Part of Decks, Fences & Roofing
Quick answer
Hold a level horizontally against the roof, mark 12 inches along it, then measure straight down from that mark to the roof surface. That drop in inches is the pitch — a 6-inch drop over 12 inches is a 6-in-12 pitch. You can do this on the roof, on a gable rafter, or against a level photo of the roofline.
Roof pitch is the rise over a 12-inch horizontal run. Every method below measures the same thing — how many inches the roof climbs for each foot of run — you just pick where it's safest to measure.
Method 1 — Level and tape on the roof
- Set one end of a 12-inch (or 24-inch) level on the roof and hold it dead level.
- At the far end of the level, measure straight down to the roof surface.
- That measurement is the rise. Over a 12-in level it's your pitch directly; over a 24-in level, halve it.
Method 2 — From inside the attic
- Press the level horizontally against the underside of a rafter.
- Measure down 12 inches and then up to the rafter — same rise-over-12, no ladder on the roof.
- This is the safest way and works in any weather.
Method 3 — Speed square
- Place a speed square's pivot on the rafter's edge and let it hang plumb on a level line.
- Read the degree or pitch scale where the rafter edge crosses it.
- Quick for a rough number, but the level-and-tape method is more precise.
Once you have the rise and run, the roof pitch calculator converts it to pitch (x-in-12), the angle in degrees, the grade percentage and the slope factor — and gives you rafter length if you enter the horizontal run.
FAQs
Can I measure roof pitch from the ground?
Roughly, yes — take a level side-on photo of the gable end, then measure the rise and run on the photo (or with a phone pitch app). It's good for an estimate; for ordering material, confirm with a level-and-tape measurement.
Do I measure pitch over 12 inches or 12 feet?
Always 12 inches of horizontal run. Pitch is written as rise-in-12, like 6-in-12, where both numbers are inches. A 6-in-12 roof rises 6 inches for every 12 inches of run.