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INCLINOMETER

An inclinometer in your pocket

An inclinometer measures how steeply a surface tilts from level. Your iPhone already has the sensor for it — the Protractor app turns it into a slope meter that reads any incline in degrees, percent grade, or the X-in-12 ratio builders use. Rest the phone on the slope and read the number.

Inclinometer, clinometer, slope meter — same tool

The names vary by trade: surveyors and foresters say clinometer, builders and vehicle owners say inclinometer, and everyone else says slope meter or tilt meter. They all do one thing — report the angle of a slope relative to level. Traditional versions use a weighted needle or a curved liquid vial; a digital inclinometer uses an electronic tilt sensor, which is exactly what the accelerometer in your iPhone is.

Degrees, percent grade, or ratio — without re-measuring

Slopes get quoted three ways: degrees (a 5° driveway), percent grade (an 8% hill — rise over run × 100), and ratio (a 4:12 roof pitch). The app shows the same reading in any of the three with a tap, so you can check a wheelchair ramp against the 8.33% ADA limit, a drainage grade against a 2% minimum, or a rafter against the plans — with one measurement.

Where a phone inclinometer earns its keep

Ramps and driveways, deck and gutter drainage, RV and camper leveling, off-road pitch and roll, stair stringers, attic rafters, and any hillside you can lay a phone on. For slopes you can't reach, the camera mode measures the incline from a photo instead. The full technique — including zeroing against a reference surface — is in how to measure slope and incline, and the sensor detail is on how it works. Need level rather than slope? The same app is a digital spirit level too.

FREQUENTLY ASKED QUESTIONS

What is an inclinometer?

An inclinometer (also called a clinometer, tilt meter, or slope meter) measures how far a surface tilts from level, usually in degrees or percent slope. Traditional ones use a weighted needle or a liquid vial; digital ones use an electronic tilt sensor — the same kind of accelerometer built into every iPhone.

Is there a free inclinometer app for iPhone?

Yes. The Protractor app works as an inclinometer: rest the iPhone on a slope and it reads the incline live in degrees, percent grade, or an X-in-12 ratio. It is free to download and try, works offline, and has no ads.

What is the difference between an inclinometer and a clinometer?

Nothing meaningful — they are two names for the same instrument. "Clinometer" is more common in surveying and forestry, "inclinometer" in construction and vehicles. Both measure the angle of a slope relative to level.

How accurate is a phone inclinometer?

Once the phone sits flat on the surface and the reading settles, expect accuracy within about a degree — plenty for ramps, driveways, drainage grades, roof pitch, and RV or 4x4 leveling. For engineering-grade survey work, use a calibrated instrument.

How do I measure the slope of a ramp or driveway?

Lay the phone along the slope in the direction of travel and read the incline. Percent grade is rise over run × 100 — an ADA-compliant ramp, for instance, must not exceed 8.33% (1:12, about 4.8°). Tap the readout to switch between degrees, percent, and ratio without re-measuring.

Can I measure a slope I can’t reach?

Yes — use camera mode. Point the iPhone at the hillside, roofline, or ramp, drag one on-screen arm along the horizontal and the other along the slope, and read the angle between them. It works on saved photos too.

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