Digital Protractor

The device tilt mode is selected when this page opens. On an iPhone or iPad, iOS asks for motion access the first time you press the enable button – the browser is not permitted to start those sensors without an explicit tap. On most Android phones and desktop browsers no permission is needed, and the reading begins by itself.

Two numbers come out of the sensor. Pitch (beta) is the forward-and-back tilt, roll (gamma) is the side-to-side lean, and the main readout follows pitch. Press zero while the phone rests on your reference surface – a desk, a shelf, a deck board – and every later reading is measured from that starting point instead of from the factory orientation.

Let the value settle before you trust it. Sensor data arrives many times a second and jitters by a few hundredths of a degree while anything moves, so rest the case flat against the surface instead of holding it, keep your fingers off the screen, and take the number once the bubble stops drifting.

Case thickness and uneven surfaces are the usual sources of error: a case with a raised lip rocks slightly and the reading wanders with it. Zero on the surface you trust and measure at the same spot. For anything structural – a footing, a handrail, a load-bearing slope – confirm the result with a spirit level or a proper inclinometer. This is a fast field check, not a calibration certificate.

Checking that a shelf, a fence post or a picture rail is plumb; reading the fall across a patio or a shower base before the tiles go down; setting the tilt of a solar panel; confirming a ramp sits within the angle the code allows. Anywhere you would previously have fished a bevel gauge out of the toolbox, the phone gives you a number in a second.

The side panel reports slope as a percentage as well as an angle, which is the language most building codes and road signs use. Every locked reading can be saved to the measurement history in this browser and exported as a CSV file, so a day of checks becomes a table you can attach to a report.