Accelerometer Test

How to test your phone's accelerometer

1. Open this page on the phone and tap Start accelerometer test. On iPhone, tap Allow in the motion access prompt.
2. Tilt the phone slowly. With gravity on, the line for the axis pointing up rises towards 9.8 and the others fall towards 0.
3. Switch to Movement only and shake the phone. The graph should spike and the shake counter should count each shake.
4. Lay the phone flat on a table and tap Gravity check. Keep still for 5 seconds and read the result.
5. Turn the phone sideways and compare Sensor says with Screen is to see whether an auto-rotate problem is the sensor or a setting.

What the results mean

An accelerometer measures acceleration in metres per second squared (m/s²) along three axes. Even lying still it feels gravity, so a phone flat on a table should read about X 0, Y 0, Z 9.81, which is 1 g in total.

• Gravity check within 0.35 of 9.81: accurate. Phone sensors are often a few percent off, and up to 0.7 is still normal.
• X or Y above 0.5 while flat: the surface is not level, or the sensor has an offset. A level table and a second run tell the two apart.
• Total far from 1 g while still, or values frozen: a faulty sensor or a browser that blocks it.
• Peak: the highest total seen. A firm shake gives 2 to 3 g; most phone sensors cap at 8 or 16 g.
• Sensor says landscape, screen stays portrait: the sensor works and the problem is the rotation setting or the app.

Movement only removes gravity, so it reads about zero when the phone is still and shows just the shaking or the motion of a car or a lift.

The three axes

Hold the phone upright in portrait, screen facing you. X runs left to right across the screen, Y runs from the bottom to the top, and Z comes out of the screen towards you. The browser uses the same directions on every phone. Safari on iPhone has long reported these readings with the opposite sign, so this page checks the sign against the tilt angles and corrects it, keeping the numbers the same on iPhone and Android.

The accelerometer cannot tell how fast the phone is turning, only which way gravity pulls and how hard the phone is pushed. Turning is the job of the gyroscope; see gyroscope vs accelerometer and the gyroscope test.

What the accelerometer is used for

Auto-rotate, the step counter, shake gestures, lift to wake, fall and crash detection, tilt games and the spirit level all start from the accelerometer. If several of these stop working at the same time, test the sensor here first. The bubble level uses the same sensor to show whether a surface is flat.

Common problems and fixes

No data on the phone

In Chrome on Android, tap the lock icon by the address, open Permissions and allow Motion sensors. On iPhone, close Safari fully and reopen the page so the Allow prompt appears again. Battery saver modes on some Android phones also pause sensors in the browser.

Auto-rotate does not work but the sensor does

If "Sensor says" changes when you turn the phone, the accelerometer is fine. Turn on Auto-rotate (Android quick settings) or turn off Portrait Orientation Lock (iPhone Control Centre). Some apps and home screens never rotate.

The values are frozen or jump wildly

Restart the phone. If the gravity check still fails flat on a table, try the sensor test menu: Samsung phones open it by dialling *#0*# and tapping Sensor. A sensor that fails there too needs a repair.

Steps or shake gestures are not counted

Check the app has the physical activity permission (Android) or Motion & Fitness access (iPhone Settings > Privacy & Security). If the shake counter here works, the sensor is fine.