Your phone's motion sensor measures real tilt, not a ruler drawn on the screen. Lay the phone on a shelf or hold it against a frame, watch the bubble settle, and listen for the beep when the surface is level.
Start the level
This level reads your phone's tilt sensor to check shelves and frames. On iPhone, you will be asked to allow motion access on the next screen.
How a Phone Bubble Level Works
Phones contain motion sensors that detect which way gravity points. This page reads those sensors through your browser and turns the result into a live tilt angle and a moving bubble, like the vial in a classic spirit level. No app install is needed.
A ruler or protractor drawn on screen only gives you a scale to hold against something. This page measures how the phone itself is tilted, so the number reflects the surface the phone is touching.
Choose Lay flat for shelves, tables, and appliance tops, or Hold upright for picture frames and walls. When the reading falls inside your tolerance, the bubble turns green, the page shows a level status, and it plays a short beep. If your browser supports vibration, the phone also buzzes briefly.
You can read tilt in degrees, as slope percent, or in inches per foot. A span field also converts the current tilt into inches of rise over any length you enter, so you can see how far one end of a shelf is off.
Jobs You Can Check with Your Phone
Bookcases, TV stands, and tables
Set the phone on the top surface in Lay flat mode and adjust the feet or shims until both readings are near zero. Useful for furniture that rocks or leans.
Floating shelves and wall brackets
Check the shelf board after mounting, or rest the phone on the board while you adjust the bracket. The span field shows how much one end sits high or low over the shelf length.
Picture frames, mirrors, and clocks
In Hold upright mode, press the phone against the frame and watch the side-to-side reading. Adjust the frame until it is close to zero, then check again after you let go.
Washers, fridges, and patio furniture
Place the phone on top of the appliance or table and turn the leveling feet until the bubble centers. Save a reading at each corner to compare them.
How to Check a Shelf or Frame in 5 Steps
- Open the page on a phone. On an iPhone, tap the start button and choose Allow when Safari asks about motion access.
- Pick a mode: Lay flat for shelves and furniture, or Hold upright for frames and walls.
- Put the phone flat on the surface, or press it upright against the frame, and watch the bubble and the two tilt readings.
- Adjust the object until the bubble is inside the center ring. When the reading is within your tolerance, the bubble turns green and you hear a beep.
- If a surface you trust does not read zero, tap Set zero. Use Save reading to store a value at each spot you check.
Note: For a steadier reading, take off the phone case, turn on rotation lock, and press the phone flat against the surface.
Limits to Know Before You Drill
- The page needs a phone or tablet with a motion sensor. Most laptops and desktops do not have one, so the level will not work on them.
- Phone sensors vary and are less precise than a dedicated level. Use the 180-degree flip check in the guide below to see how far off your phone is.
- On iPhone, Safari must be allowed to use motion sensors. Without that permission, no angle or bubble appears.
- The Hold upright mode uses the side-to-side reading to decide whether the surface is plumb. The front-to-back reading is shown for reference only.
- Saved readings stay in the page's memory only. Reloading or closing the page clears them, and the list holds up to 20 readings.
Tilt Angle to Rise: Inches per Foot and mm per Meter
How much height difference a given tilt creates. The values come from the tangent of the angle, so you can use them to judge what a reading means for your shelf or frame.
| Angle | Rise per foot (in) | Rise per meter (mm) | Slope (%) |
|---|---|---|---|
| 0.1° | 0.02 | 1.7 | 0.17% |
| 0.5° | 0.10 | 8.7 | 0.87% |
| 1° | 0.21 | 17.5 | 1.75% |
| 2° | 0.42 | 34.9 | 3.49% |
| 3° | 0.63 | 52.4 | 5.24% |
| 5° | 1.05 | 87.5 | 8.75% |
| 10° | 2.12 | 176.3 | 17.63% |
| 15° | 3.22 | 267.9 | 26.79% |
| 20° | 4.37 | 364.0 | 36.40% |
| 30° | 6.93 | 577.4 | 57.74% |
Example:
A 36-inch shelf tilted by 1° has one end about 0.63 inch higher than the other. A 48-inch shelf at the same angle is off by about 0.84 inch. The longer the object, the more a small angle shows.
Sensor Basics, iPhone Permission, and Getting a Steadier Reading
What the phone is measuring, how to turn on motion access on iPhone, and how to check and improve your results.
What the tilt sensor measures
Phones combine an accelerometer, which senses gravity, with a gyroscope, which senses rotation. This page asks the browser for the device's orientation angles through the standard DeviceOrientation interface and smooths them slightly so the bubble does not jitter.
The page then converts the angles into a side-to-side tilt and a front-to-back tilt, adjusting for portrait or landscape.
How to allow motion access on iPhone
Safari on iOS 13 and later asks before a site can read motion data. Tap the start button on this page and choose Allow.
If you chose Don't Allow, open Settings, go to Safari (newer iOS versions list it under Apps), turn on Motion & Orientation Access, and reload the page. If the prompt still does not appear, clear this site's data in Safari's Advanced settings and try again.
A 180-degree flip check to find your phone's offset
Put the phone on a flat surface and note the side-to-side reading. Turn the phone 180 degrees in place without moving the surface, and read it again. If the two numbers match, your phone has little offset for that axis. If they differ, the sensor is off by about half the difference.
Once you know the offset, tap Set zero on a surface you trust, or subtract the offset from your readings.
Lay flat versus Hold upright
Lay flat is for horizontal surfaces. Both the side-to-side and front-to-back readings need to be within your tolerance for the level status to appear.
Hold upright is for vertical surfaces such as frames. The level status depends on the side-to-side reading, and the front-to-back reading shows how far the phone leans away from upright.
Common Mistakes When Leveling with a Phone
No angle appears on an iPhone
The motion-access prompt was missed or declined, so the page never receives sensor data and the bubble stays still.
💡 See the solution▼
Readings jump when the screen rotates
The phone switches between portrait and landscape while you measure, and the numbers change for a moment.
💡 See the solution▼
Measuring with a thick case or on an uneven spot
A bulky case, a raised edge, or a dirty spot on the shelf keeps the phone from sitting flat, so the reading reflects the case and not the surface.
💡 See the solution▼
Skipping calibration
Every phone sensor has a small offset, so a perfectly level surface may not read 0°. Leveling a shelf to that reading builds the offset into the job.
💡 See the solution▼
Trusting a phone for precision work
Phone sensors are not built for tight tolerances, so relying on one for structural or finish carpentry can leave visible errors.
💡 See the solution▼
Questions About Accuracy, Permissions, and Calibration
Q.Do I need to allow motion access on an iPhone?
A. Yes, on iPhones running iOS 13 or later, Safari asks for permission before a web page can read the motion sensors. Tap the start button on this page and choose Allow. If you tapped Don't Allow, open Settings, find Safari (newer iOS versions list it under Apps), turn on Motion & Orientation Access, and reload the page. If the prompt still does not come back, clearing this site's data in Safari's Advanced settings resets the choice. On Android and most other browsers, no prompt is needed and the level starts as soon as the page loads.
Q.How accurate is a phone level compared with a real spirit level?
A. A phone's tilt sensor is less precise than a dedicated bubble vial or laser level, and the error varies from phone to phone. This page cannot measure your phone's error for you, but you can check it yourself: set the phone on a flat surface, note the reading, turn the phone 180 degrees in place, and read it again. If the two readings are different, the sensor is off by about half the difference. For hanging shelves and frames this is usually enough. For framing, tile, or anything that needs tight tolerances, use a dedicated level.
Q.Why does the reading not show 0° on a surface that looks flat?
A. Either the surface is slightly off or the sensor has a small offset. Place the phone on a surface you trust, such as a checked countertop, and tap Set zero. The tool then treats that position as 0° and shows every later reading relative to it. Switching between Lay flat and Hold upright clears the calibration, so set zero again after you change modes.
Q.What is the difference between Lay flat and Hold upright?
A. Lay flat is for horizontal surfaces such as shelves, tables, and appliance tops. Put the phone on the surface and bring both the side-to-side and front-to-back readings close to zero. The tool reports level only when both are inside your tolerance. Hold upright is for vertical surfaces such as picture frames and walls. Hold the phone upright against the surface. In this mode the level status depends on the side-to-side reading, and the front-to-back reading shows how far the phone leans away from upright.
Q.Does screen rotation affect the reading?
A. The tool adjusts its axes for portrait and landscape, so the side-to-side and front-to-back labels stay consistent. If the screen flips while you are measuring, the numbers can jump for a moment. Turn on your phone's rotation lock before you start to avoid that.
Q.What does the tolerance setting change?
A. Tolerance sets how close to zero a reading must be before the tool shows the level status and plays the beep. You can set it from ±0.2° to ±2.0°, and it starts at ±0.5°. A tolerance of 0.5° is about 0.10 inch of rise per foot. A smaller tolerance is stricter and harder to hit by hand.
Q.Why do I not hear a beep or feel a vibration?
A. The beep plays once each time the reading moves into your tolerance, so you will not hear it again until you move out and back in. Check that your phone volume is up and the Beep when level switch is on. Vibration works only in browsers that support it. If yours does not, the tool shows a note under the vibration switch and turns it off.
Q.Does this work on a laptop or desktop?
A. Only if the device has a motion sensor. Most laptops and desktops do not, and the page will tell you the device has no tilt sensor. Open the page on a phone or tablet instead.
Q.Are my readings sent anywhere?
A. No. The tilt readings are read and calculated in your browser, and this tool does not send them to a server. Saved readings are held in the page's memory only, up to 20 at a time, and are gone when you reload or close the page.
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