How to use the Bubble Level
- Open this page on your phone and tap Enable sensors (iPhone and iPad ask for motion & orientation access).
- Lay the phone flat for surfaces, or switch to Edge mode and hold its side against an object for vertical edges.
- If the case or camera bump tilts the phone, place it on a known level surface and tap Calibrate.
- Once stable, tap Hold reading and pick up the phone to read it.
How a web bubble level works
The phone’s accelerometer and gyroscope report front-back tilt (beta) and left-right tilt (gamma) through DeviceOrientation events. The tool converts both into a bubble position and total tilt, with 0.0° meaning level. Typical phones repeat within 0.1°–0.5°, fine for DIY and hanging pictures; use a professional level for precision work.
Why calibration matters
Camera bumps, cases and sensor zero offsets can keep a flat phone from reading 0. Place it on a known level surface and tap Calibrate; the tool remembers the offset on this device and subtracts it from later readings.
Compass and browser limits
Compass heading comes from the magnetometer and drifts near metal, magnets and electronics; move the phone in a figure-eight to recalibrate. iOS Safari requires a tap to allow sensors, and most computers have no such sensors, which the tool reports.
Frequently asked questions
Does it work on a computer?
Most computers have no orientation sensor, so it will not work. Open the page on a phone or tablet.
Nothing happens on my iPhone
iOS 13 and later need you to tap Enable sensors and allow access. If you denied it earlier, close the Safari tab and reopen it, or check Motion & Orientation Access in Settings → Safari.
How accurate is it?
Typical phones repeat within 0.1°–0.5° depending on the sensor and case. After calibration, comparisons on the same phone are most reliable.
How do I measure a slope or roof angle?
Hold the phone’s edge against the slope in Edge mode to read the angle, or use the total tilt in Surface mode.
Is the compass accurate?
Nearby magnetic fields interfere. Move away from computers, speakers and steel, do the figure-eight calibration and rely on a mapping app for navigation.