A LEVEL IN YOUR POCKET
Online bubble level for your phone
Use this free online spirit level to check a surface, wall or slope with your phone.
Works with your phone’s motion sensor. No download or sign-in.
Lay the phone screen-up on a shelf or tabletop.
Target angle: 0.0°
Tap Start level on your phone to read its motion sensor.
For flat surfaces, place the phone screen-up and let it rest. Remove a bulky case if it rocks.
Using a computer? Open on your phone
Scan this code with your phone camera. No app needed.
https://bubblelevelonline.com/GET A USEFUL READING
Three small steps
- 01
Choose your position
Use Flat surface with the phone screen-up on a table. Choose Edge / wall for a frame or vertical surface, with the screen facing you.
- 02
Start & let it settle
Tap Start level and allow motion access if your browser asks. Wait for the reading to say “Steady.”
- 03
Adjust the high edge
Follow the direction below the bubble, then check again. Set zero only when comparing against a chosen reference surface.
WHAT IT SHOWS
A spirit level, in your browser
Flat surface shows both tilt axes. Edge / wall checks level or plumb. Slope / angle measures along the phone’s long edge, shows grade and rise:run, and guides you to a target angle. Positive slope means the phone’s top end is high. All modes use your phone’s accelerometer; uneven contact can change the result.
BEFORE YOU TRUST IT
Quick check, sensible limits
Phone sensors, cases, camera bumps and uneven contact can shift a reading. Set zero on a reference you trust if you are comparing surfaces. For construction, safety, or precision work, use a calibrated physical level.
Which bubble level mode should I use?
A bubble level and a spirit level describe the same kind of level-checking tool. This version uses your phone’s motion sensor. Choose the mode that matches how the phone touches the object.
Flat surface: two-axis level
Rest the phone screen-up on a tabletop or shelf. Watch left–right and top–bottom tilt together. Check another position too: a phone only measures where it rests.
Edge / wall: level or plumb
Keep the screen facing you and place a straight phone edge against a picture frame or wall. Plumb means vertical; level means horizontal. Follow the rotation guidance.
Slope / angle: inclinometer
Rest a long phone edge along an incline to read degrees, slope percentage and rise:run. Set a target such as 45° to compare angles. Positive means the phone’s top end is higher.
Need help placing your phone? Read the phone level setup guide or the slope and target-angle instructions.
Degrees and slope percentage are different
In Slope / angle mode, grade (%) = 100 × tan(angle), with the angle expressed in degrees. A 45° slope is 100% grade because rise and horizontal run are equal.
| Angle | Slope / grade |
|---|---|
| 0° | 0.0% |
| 1° | 1.7% |
| 5° | 8.7% |
| 45° | 100.0% |
A negative value means the phone’s top end is lower. Vertical shows “Vertical” instead of an infinite percentage. After Set zero, results are relative to that reference. Reset zero before checking an absolute slope.
Before using your phone as a level
Do I need to install an app?
No. Open the online level in a supported phone browser, tap Start level and allow motion access if asked. A desktop without a sensor cannot produce a real reading.
How do I calibrate the bubble level?
Wait for a steady reading on a chosen reference, then tap Set zero. This compares positions; it does not prove that the reference is level. See what calibration changes.
Can I use it without internet?
Tap Save offline while connected and wait for confirmation. The tool and guides can then reopen in that browser without internet, unless the browser clears its saved files.
For sensor permissions, frozen readings and accuracy limits, see the bubble level FAQ and measurement limitations.