Bubble Level: Check Any Surface

How to use the bubble level

1. Tap Start level and allow motion access if your phone asks.
2. Lay the phone flat on the surface, screen up.
3. When the bubble sits inside the ring and the tilt reads 0.0°, the surface is level.

The left and right reading shows tilt across the width of the phone, and the front and back reading shows tilt along its length. The bubble always floats towards the higher side, just like the bubble in a traditional spirit level.

Calibrate for best accuracy

Phone sensors are rarely perfectly zeroed, and a bulging camera bump can tip the phone slightly. Place the phone on a surface you know is level, such as a good worktop, and tap Calibrate. The level then reads relative to that surface. Hold freezes the reading, which helps when you cannot see the screen.

What it is good for

• Hanging pictures and mirrors
• Putting up shelves
• Levelling a washing machine, table or camping van
• Checking the slope of a patio or desk

For precise building work, a long spirit level or laser level is still the right tool. For quick everyday checks, your phone is surprisingly good, typically to within about half a degree after calibration. See also the compass, which uses the same motion sensors.

Degrees, percent and slope

Builders often talk about slope as a percentage or a ratio rather than degrees. A slope of 1° rises about 1.75 cm for every metre, or 1.75 percent. A 2 percent fall, the usual minimum for a patio or shower floor to drain, is about 1.15°. A wheelchair ramp at a ratio of 1 in 12 is about 4.8°.

The level shows total tilt as well as the two axes, so you can see at a glance how far out a surface is, then use the left and right and front and back readings to work out which leg, shim or bracket to adjust first.