Bubble Level
Free online bubble level. Turn your phone or tablet into a spirit level: live tilt angles in degrees, combined tilt readout and zero calibration on any surface.
How does a phone bubble level work?
Phones contain an accelerometer that senses gravity. The tool converts the beta and gamma orientation angles into left-right and front-back tilt in degrees and shows a virtual bubble moving on a target.
Does it work on a computer?
Desktops and laptops without motion sensors cannot provide tilt data, so the tool shows guidance instead. Use a phone or tablet for actual measuring.
Why does iOS ask for permission?
Since iOS 13, browsers must ask explicit permission before accessing motion sensors. Press "Start sensor" and allow the request; then place the device on the surface.
What does "Zero calibrate" do?
It sets the current position as the reference. This is useful for checking that a surface is parallel to a sloped reference — the bubble centers once the device matches the calibrated plane.
How accurate is it?
Typical phone accelerometers resolve a fraction of a degree. For visual checks of shelves, tripods, pictures and appliances it is more than sufficient; for certified construction work use a real level.
How do I measure a slope with it?
Place the device on the known-level surface, tap "Zero calibrate", then move it to the surface being tested. The displayed angle is the deviation from your calibrated reference.
Is any data collected?
No. Sensor values are read in your browser and used only for the on-screen display. Nothing is recorded, stored or uploaded.
How flat is "level"?
The bubble turns green and the "Level!" indicator appears when both axes are within about 1.2 degrees — precise enough for everyday alignment tasks.
How to Use Bubble Level
This bubble level turns your phone or tablet into a spirit level entirely in your browser: motion sensor data is read locally to show left-right tilt, front-back tilt and a combined angle, with a virtual bubble on a target. Nothing is uploaded.
- Tap "Start sensor" — on iOS 13+ also allow the motion permission request.
- Place the device flat against the surface you want to check, long edge down.
- Watch the bubble: it moves with the tilt and turns green when both axes are within about 1.2 degrees.
- Read the exact angles in the three boxes: left-right, front-back and combined tilt.
- To check a slope against a known reference, rest the device on the reference and tap "Zero calibrate", then compare the second surface.
A phone lying flat on a picture frame tells you instantly if it hangs straight — no nails or string level needed.
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