Bubble level
Lay your phone flat on a shelf, table or frame and press Start. The bubble moves to the high side and the readings show how many degrees you are off on each axis. It needs a motion sensor, so it works on phones and tablets rather than most desktops.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Press Start and allow motion access if the browser asks.
- Place the phone flat on the surface you want to check. Keep the case off if it is thick or uneven.
- Read the two angles. A positive left–right value means the right edge is lower; a positive front–back value means the top edge is higher.
- To remove any sensor error, put the phone on a surface you trust and press Set zero here.
How it works
The browser reports the phone’s rotation as beta (front to back) and gamma (left to right) in degrees. The page subtracts your saved zero from both, draws the bubble toward the high side, and shows the total tilt as √(x² + y²). The slope is tan(angle) × 100, the same percent grade used for roads and ramps. Nothing runs between sensor updates and nothing is sent anywhere.
Worked example
If the left–right reading is 3.0° and the front–back reading is 4.0°, the total tilt is √(9 + 16) = 5.0°, which is a slope of tan(5°) × 100 ≈ 8.7 %.
Tips
- Phone sensors are good to about a degree. Use a real level for work that needs better.
- Turn the phone 180° and check again: if the readings change sign, the surface is level and the sensor has a small offset, which Set zero removes.
Frequently asked questions
Why does it say there is no sensor on my computer?
Most desktop and laptop computers have no orientation sensor, so the browser sends no tilt data. The tool waits about a second and then shows a message. Open the page on a phone or tablet instead.
Why does my iPhone ask for permission?
Safari on iPhone and iPad only shares motion and orientation data after you agree. The request appears when you press Start, and you can accept it for this visit.
How do I make it accurate?
Put the phone on a surface you know is level, such as a good spirit level or a freshly checked shelf, and press Set zero here. Every reading is then measured from that position, which cancels small sensor errors and a case that is not perfectly flat.
Can I measure a wall or a vertical surface?
No. The dial is designed for a phone lying flat, where the sensor angles map directly to tilt. A phone standing upright reports a different set of angles, so the readings would not mean what the labels say.