How to Measure Roof Pitch: 3 Easy Methods
Knowing your roof's pitch is essential before ordering materials, getting contractor quotes, or planning any roofing project. The good news is that you don't need specialized equipment or professional training to measure it yourself. There are three reliable methods — and at least one of them works from the comfort of your attic without ever stepping outside.
This guide walks through each method step by step, from the most common (a level and tape measure) to the quickest (your smartphone).
What You're Measuring
Roof pitch is expressed as the number of inches the roof rises vertically for every 12 inches of horizontal run. A 6:12 pitch rises 6 inches per foot. All three methods below ultimately produce those two numbers — the rise and the 12-inch run — whether directly or by converting from an angle.
If you want to skip the manual measurement entirely, plug your numbers into our Roof Pitch Calculator once you have them.
Method 1: Level and Tape Measure (From Outside)
This is the most common method and works from the ground level or from a ladder positioned at the eave. All you need is a standard carpenter's level (at least 12 inches long) and a tape measure.
Tools needed:
- Carpenter's level (12" or longer)
- Tape measure
- Pencil or marker (optional)
- Ladder (for single-story roofs, a 6-foot ladder is usually sufficient)
Steps
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Set up your ladder safely at the edge of the roof, positioned so you can reach the lower portion of the roof slope without climbing onto the roof surface itself. For most single-story homes, you can do this from an extended reach. For two-story homes, measure from the attic instead (see Method 3).
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Place the level against the roof surface with one end touching the shingles. Hold it so it runs along the slope of the roof — not flat against the fascia board.
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Level the tool. Adjust until the bubble in the level is perfectly centered. The level is now running horizontally, which means one end is lifted away from the roof surface and the other is touching it.
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Mark the 12-inch point. From the end where the level touches the roof, measure exactly 12 inches along the level toward the raised end. Mark this spot on the level with a pencil or simply hold your finger there.
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Measure the vertical gap. At the 12-inch mark, measure straight down from the bottom edge of the level to the roof surface below. Use your tape measure held perfectly vertical for accuracy.
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Record your pitch. The vertical measurement in inches is your rise. Write it down as X:12. If the gap was 5 inches, your pitch is 5:12.
Tips for Accuracy
- Make sure the level is truly horizontal before measuring down — even a small tilt throws off the result.
- Measure at a clean section of roof, away from ridge caps, vents, or flashing.
- Take two or three measurements at different spots and average them for best accuracy.
- If you have a 24-inch level, you can still measure from the 12-inch mark for consistency.
Method 2: Smartphone App (Quickest Method)
Modern smartphones have a built-in accelerometer and gyroscope that can measure angles with surprising accuracy. The iOS Measure app (on iPhones running iOS 12 or later) includes a level feature, and many Android phones have a similar tool in the built-in Compass or Level app. Alternatively, free third-party apps like Clinometer are purpose-built for measuring roof pitch.
Tools needed:
- Smartphone with a level or clinometer app
- A straight edge or ruler (optional, to rest the phone on)
Steps
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Open your level or clinometer app. On iPhone, open the Measure app and tap the Level tab at the bottom. On Android, open the Compass app and look for a Level mode, or download a free clinometer app from the Play Store.
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Calibrate if prompted. Some apps ask you to hold the phone flat on a level surface to calibrate before use. Follow the on-screen instructions.
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Access the roof slope. You can measure from the roof surface itself, from the rake board on the side of your home (the angled trim that follows the roofline), or from the underside of a rafter inside the attic. The key is that the surface you're placing the phone against must follow the exact angle of the roof.
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Place the phone flat against the surface. Lay it with its edge (long side) running along the roof slope. Hold it steady and note the angle reading on screen.
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Convert degrees to pitch. Most clinometer apps will give you the angle in degrees. Use the following conversion:
- 14° ≈ 3:12
- 18° ≈ 4:12
- 22° ≈ 5:12
- 27° ≈ 6:12
- 30° ≈ 7:12
- 34° ≈ 8:12
Or use our Roof Pitch Calculator — enter the angle and it instantly shows you the X:12 pitch.
Tips for Accuracy
- Hold the phone as still as possible and wait for the reading to settle before recording.
- Measuring against the rake board is often easier and safer than climbing onto the roof.
- On textured or rough surfaces (like cedar shakes), rest the phone on a short, straight piece of wood placed against the surface for a cleaner reading.
- Cross-check with one other measurement if precision matters, since phone accelerometers can drift slightly.
Method 3: From Inside the Attic with a Rafter Square
If you have attic access, this method is both safe and highly accurate — no ladders, no outdoor climbing. A rafter square (also called a speed square or framing square) is designed for exactly this kind of measurement and is a staple tool in any carpenter's bag.
Tools needed:
- Rafter square (speed square or framing square)
- Tape measure or ruler
- Flashlight or headlamp
Steps
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Access the attic. Use the attic hatch or pull-down stairs. Bring a flashlight and wear a dust mask if your attic has blown-in insulation.
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Find an exposed rafter. Look for one of the diagonal boards running from the ridge beam at the top to the wall plate at the bottom. These are the structural members that follow the exact slope of the roof.
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Position the rafter square. Hold the square against the side of the rafter with the pivot point (the corner of the square) touching the rafter. Orient it so the long arm (the "blade") runs horizontally and the short arm (the "tongue") runs vertically.
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Read the pitch directly. Many rafter squares have pitch markings printed on them. Align the blade of the square so it runs level (you can verify this with a small torpedo level or your smartphone), then read where the rafter crosses the inch markings on the tongue of the square. That number is your rise.
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Record your pitch. If the rafter crosses the tongue at the 7-inch mark, your roof pitch is 7:12.
Tips for Accuracy
- A small torpedo level placed on the blade of the square confirms it's horizontal before you take the reading.
- Measure at least two different rafters in different parts of the attic to confirm consistency.
- Be careful where you step — in most attics, you can only safely walk on the joists (the horizontal boards). Never step between them onto the drywall ceiling below, as it cannot support your weight.
Safety Tips
Measuring roof pitch can involve ladders, attic spaces, and roof surfaces. Follow these precautions to stay safe:
- Never work on a wet or icy roof. Even low-pitch roofs become dangerously slippery when wet.
- Use a ladder with non-slip feet set at the proper angle (about 75 degrees from horizontal). Have a second person hold the base when possible.
- Do not climb above the eave line unless you are trained in roof safety and have appropriate fall protection equipment.
- In the attic, step only on joists, not on the insulation or drywall between them.
- Wear a headlamp in the attic — free hands are safer hands.
- If the roof is steep (above 7:12), do not attempt to walk on it without proper harness and anchor equipment. Consider measuring from the attic or asking a professional.
- On hot summer days, roof surfaces can reach 150°F or more. Wear gloves and closed-toe shoes if you must touch the shingles.
Which Method Should You Use?
| Method | Best For | Equipment Needed | Safety Level | |---|---|---|---| | Level & tape measure | Most accurate outside measurement | Level, tape measure, ladder | Moderate — stay below the eave | | Smartphone app | Quickest; no special tools | Smartphone | High — can measure from ground or rake board | | Rafter square in attic | Safest; no outdoor ladder | Rafter square, flashlight | High — stay on joists |
For most homeowners, the smartphone app is the fastest starting point. If you need a verified measurement for a material order or contractor quote, follow up with the level and tape measure method or the attic rafter square method for confirmation.
Once you have your rise measurement, enter it into our Roof Pitch Calculator to get your pitch in X:12 notation, degrees, and slope percentage — all at once.