How to use your phone as a level
Level is a free spirit level and bullseye level that runs in your phone's browser. It reads the motion sensors already inside your phone to show how level, or how plumb, a surface is. It works offline once loaded, and nothing you measure ever leaves your device.
Getting started
- Open isitlevel.app in Safari on iPhone or Chrome on Android.
- Tap Enable sensors. On iPhone, iOS will ask permission to use Motion & Orientation.
- Set the phone against the surface you want to check. Level picks the right display automatically depending on how the phone is positioned.
To keep it on your home screen, use your browser's Add to Home Screen option. Once loaded, the app works without a connection, which is handy in a basement, garage or job site with no signal.
The three modes
Lying flat: bullseye level
Place the phone flat on a table, shelf, floor or worktop, screen up or screen down. A bubble moves across a circular dial toward the high side, just like the bullseye vial on a tripod or a camera hot shoe. When the bubble settles inside the centre ring, the surface is level and the display glows. The bullseye reads level within 1.0°.
Standing on an edge: spirit-level vial
Stand the phone on any of its four edges against a wall, door frame, picture or a length of pipe. The display rotates itself so it always reads the right way up, and shows a classic tube-style vial. The bubble shows the left-right lean, and a small gauge shows any front-to-back tilt. The vial reads level within 0.4°. This is the mode to use to check that something is plumb, meaning truly vertical.
Camera aim: level at a distance
Tap the aim button in the top-left corner to open the rear camera with a horizontal reticle line. The line rotates to show true level relative to whatever you point at, so you can check a ceiling line, a shelf on the far side of a room or a picture frame without touching it. The camera view is used only on screen and is stopped as soon as you close it or leave the app.
Calibrating out a small hardware offset
On some phones the motion sensor is mounted a fraction of a degree off from the screen's true axes. Smoothing cannot remove a constant offset like that, but calibration can.
- Lay the phone on a surface you know is flat.
- Press and hold the dial for about a second.
- Level stores the offset and applies it in every mode.
Calibration only works in flat mode and only when the phone is within about 8° of level, so a calibration attempt on a tilted surface or against a wall can't throw off your readings. You can clear it any time from Settings → Reset.
Getting an accurate reading
- Wait for the number to settle. The large reading dims slightly while Level is still averaging out hand movement, and firms up once the phone is still.
- Take the case off if it isn't flat, and wipe grit from the back or edge of the phone. A speck of dirt tilts the phone by more than you'd think.
- Flip and compare. Measure, turn the phone 180° on the same spot and measure again. If the two readings mirror each other, the surface is off, not the phone. If they agree, calibrate.
- Hold the reading. Tap the dial once to freeze the display so you can lift the phone and read it. Tap again to release.
- Use a straight edge for uneven surfaces. A phone sits on its camera bump and its edges, so on rough or curved surfaces lay a board or straightedge down first and put the phone on that.
A phone is a very handy level, but it is not a survey instrument. For work that needs tighter accuracy than a good hardware level, check against a proper tool.
Degrees and percent grade
Readings are shown in degrees by default. Switch to percent grade in Settings for slopes, drainage, ramps and roofs. Percent grade is the rise over the run, multiplied by 100, which is the tangent of the angle times 100.
| Angle | Percent grade |
|---|---|
| 0.5° | 0.9% |
| 1° | 1.7% |
| 2° | 3.5% |
| 5° | 8.7% |
| 10° | 17.6% |
| 45° | 100% |
You can also change how wide the display range is (Tight, Normal or Wide) to zoom in on small tilts or to cope with a rough surface.
Sound, vibration and hold
- Audio tone plays a quiet tone that rises in pitch the further you are from level, so you can level something with the screen facing away from you, including a phone lying face down.
- Vibrate at level gives a short buzz the moment you reach level, on browsers that allow vibration.
- Keep screen awake stops the display from dimming while you work.
- Colour schemes include a light one for bright outdoor conditions.
Frequently asked questions
Is Level free?
Yes. Level is free to use, with nothing to download or sign up for. If you find it useful, there may be an optional donation link, but the app works the same either way.
Does it work offline?
Yes. After the first load the app is saved on your phone and runs without a connection.
Does it collect or send any data?
No. Sensor readings are processed on your phone and are never uploaded. Your settings and calibration are stored only in your browser.
Why does my iPhone ask for Motion & Orientation access?
iOS requires every website to ask before it can read the motion sensors. Level needs them to measure tilt. If you decline by accident, re-enable it under Settings → Safari → Motion & Orientation Access and reload.
Does it work on a laptop or desktop computer?
No. Desktops and most laptops don't have the motion sensors Level needs. Open isitlevel.app on your phone or tablet.
What's the difference between level and plumb?
Level means horizontal, like a tabletop. Plumb means vertical, like a wall. Level uses the same word, "level", for both and tells you which check you're doing from the label above the reading, such as lying flat or standing · left edge down.
Why does the reading move when I set the phone down?
Level averages out small movements to give a steady number. Right after you set the phone down it takes a moment to settle, and the reading dims until it does.
How accurate is a phone as a level?
Good enough for hanging pictures, levelling shelves, appliances, campers and furniture. Accuracy depends on your phone's sensor, the surface and how clean the phone's back and edges are. Calibrate on a known-flat surface, use the flip-and-compare check above, and use a dedicated tool for precision work.