How do you measure roof pitch from the ground?

At a gable end, hold a framing square under the rake board with a level on the blade. With the blade level and touching the rake at its 12 in mark, the tongue reading where it meets the rake is the rise per 12. A reading of 6 is a 6/12 pitch.

How do you find roof pitch with a framing square?

Keep the blade level and the tongue plumb, with both legs touching the sloped surface. Read the tongue at 12 in of run on the blade. If you can't hit the 12 mark, read both legs and use 12 × tongue ÷ blade.

Can I measure roof pitch with my phone?

Yes. Lay the phone's level or inclinometer on the rake board or a rafter and read the angle, then convert: pitch = 12 × tan(angle). For example, 18.4° is about 4/12 and 26.6° is 6/12.

What is a 6/12 roof pitch in degrees?

26.57°. Pitch converts to degrees with arctan(rise ÷ run), so 6 ÷ 12 = 0.5 and arctan(0.5) = 26.57°.

MeasuringShop Math & AnglesRoof pitch from the ground

How do you find a roof's pitch without going in the attic?

Everyone tells you to go up in the attic and put a level on a rafter. It's sweltering up there, there's insulation in your collar, and the rafter you can reach is behind a duct. livin lost garage got the same advice and found the number from outside instead, with a framing square, a little level, and the rake board at the gable end.

This is ladder work at the eave. Set the ladder on firm, level ground at about 1 ft out for every 4 ft up, and keep three points of contact while you climb. Holding the square takes both hands, so get the ladder footed by a helper or tied off before you let go of the rails, and never lean out past the rails to reach the rake. Look for overhead power lines at the gable before the ladder goes up.

⚡ Rule of thumb

At the gable end, hold a framing square under the rake with a level on the blade. Keep the blade dead level and the tongue plumb, slide it until both legs touch the rake, and read the rise on the tongue at 12 in of run on the blade. That number over 12 is the pitch.

Starting point

Blade level with 12 in (305 mm) of run · tongue reading = rise per 12

Measured

Pitch = inches of rise per 12 in of horizontal run (x/12)

Confidence

Creator technique

▶ Source video — Finding pitch with a framing square — livin lost garagewatch on Facebook ↗

Applies to

Process: Roofing, siding, gutters, additions: any job that needs the existing pitch
Setup: Framing square, torpedo level, ladder
Orientation: Square held flat against the gable wall, up under the rake
Best for: Gable roofs with a straight rake board
Not for: Hip roofs (no gable rake) or rakes you can't trust to be straight

Why it matters

Pitch decides your shingle and underlayment choice, your flashing, every rafter cut, and how a new roof ties into the old one. Guess wrong and the tie-in looks wrong from the street forever.

The rake board at the gable runs parallel to the roof plane. So a level square under it reads the same number as a rafter in the attic would.

No crawling. No insulation.

What good looks like

Bubble centred on the blade at the moment you read
Both legs of the square touching the underside of the rake
Two or three readings along the rake agree within a fraction of an inch

How to apply it

Set a small level on the blade (the long leg) of the framing square.
At the gable end, hold the square flat against the wall, up under the rake, with the blade horizontal and the tongue pointing up.
Slide the square up the slope until the blade sits level and its 12 in mark touches the underside of the rake.
Keep the bubble centred and read the tongue where it meets the rake. That's the rise per 12 in of run.
Write it as a pitch: a tongue reading of 6 means 6/12.
Can't land exactly on the 12 mark? Read both legs where they touch and scale it: pitch = 12 × tongue ÷ blade. A 3 in tongue over an 8 in blade is 4.5/12.

Test it on your setup

Take the reading at two or three spots along the rake. They should match within a fraction of an inch. If they don't, the rake is sagging or the bubble drifted.
Cross-check with a phone inclinometer laid on the rake board, then convert: pitch = 12 × tan(angle). 26.6° is 6/12.
Common conversions for sanity: 4/12 = 18.4°, 6/12 = 26.6°, 8/12 = 33.7°, 12/12 = 45°. In metric it's the same ratio per 300 mm of run: 4/12 is 100 mm, 6/12 is 150 mm.

Exceptions & tradeoffs

The whole method assumes the rake trim is parallel to the roof. A sagging rake, a fascia shimmed out unevenly, or a bell-cast eave that kicks out at the bottom will all lie to you.

On a hip roof there's no gable rake to read. Use a level and tape on the roof surface, or on an exposed rafter tail, and run the same rise-over-12 math.

Mind you, if the rake has crown or built-up trim, the bottom edge might not follow the roof line. Read off the flattest board you can find.

Common mistakes

Holding the square level by eye against the rooflineWatch the bubble, not the house. Rooflines lie
Reading off the soffit (usually level) instead of the rake (sloped)Reference the sloped rake board at the gable end
Reading the tongue without the blade at 12Land the 12 in mark on the rake, or read both legs and scale to 12

Frequently asked questions

How do you measure roof pitch from the ground?At a gable end, hold a framing square under the rake board with a level on the blade. With the blade level and touching the rake at its 12 in mark, the tongue reading where it meets the rake is the rise per 12. A reading of 6 is a 6/12 pitch.
How do you find roof pitch with a framing square?Keep the blade level and the tongue plumb, with both legs touching the sloped surface. Read the tongue at 12 in of run on the blade. If you can't hit the 12 mark, read both legs and use 12 × tongue ÷ blade.
Can I measure roof pitch with my phone?Yes. Lay the phone's level or inclinometer on the rake board or a rafter and read the angle, then convert: pitch = 12 × tan(angle). For example, 18.4° is about 4/12 and 26.6° is 6/12.
What is a 6/12 roof pitch in degrees?26.57°. Pitch converts to degrees with arctan(rise ÷ run), so 6 ÷ 12 = 0.5 and arctan(0.5) = 26.57°.

livin lost garageSource & visual reference

Finding roof pitch from outside by holding a framing square with a level under the gable rake — A lot of people told me don't go in the attic. Just find it from the eaves. So here's one way to do with a square and a level! ↗ at 0:00–0:24.

Summarized and independently edited by Start Here from livin lost garage's short clip and caption, read off the frames, no audio. The level-on-the-square-under-the-rake setup is his and it's clear on screen. The exact spot he reads and the pitch he gets aren't legible in the frames, so the read-at-12 step is the standard framing-square pitch reading, not something I'm quoting from him. The scale-it formula, phone cross-check, conversions, cautions and ladder note are mine.