Skip to content
Measure & calibrate

Bubble Level

A spirit level in your browser.

Bullseye & tube views One-tap calibration Runs locally

Turn on motion sensors

Tap below and allow motion access, then place your device on the surface you want to check.

Everything runs in your browser — no motion data is uploaded.

How a phone becomes a spirit level.

Your phone packs the same idea as the glass-tube level in a toolbox, only the “bubble” is computed from sensors. The accelerometer feels the constant pull of gravity, so by reading how that pull is distributed across the device's axes, we can work out exactly how it's tilted — its pitch (front-to-back) and roll (side-to-side).

The bullseye view is for laying the phone flat on a surface, like a shelf or a tabletop: tilt in any direction nudges the bubble off-center, and it snaps green when both angles are near zero. The tube view tracks roll alone, so you can stand the phone's long edge against a wall, a picture frame or a door to check it's plumb or level.

Raw sensor data is noisy, so DeftGauge applies a light low-pass filter — each new reading is blended with the last to smooth out hand jitter without feeling laggy. And because no surface is truly flat, Calibrate lets you store the current tilt as your zero reference; the offset is kept in your browser so your level stays trustworthy next time. The dial keeps updating even with reduced-motion enabled — transitions are simply kept short.

About the Bubble Level

A bubble level is one of those tools you never think about until you need it, and then suddenly nothing on the wall looks straight. DeftGauge turns the phone or tablet already in your hand into a working spirit level, so you can check whether a surface is truly horizontal or vertical without digging through a toolbox. Instead of a sealed glass tube filled with liquid, this bubble level tool reads the tiny accelerometer and gyroscope built into your device and draws a virtual bubble that drifts away from center the moment something tilts.

How a bubble level tool works on your phone

Every modern phone contains motion sensors that constantly measure the pull of gravity. By looking at how that pull spreads across the device's axes, the tool calculates two angles: pitch (front-to-back tilt) and roll (side-to-side tilt). The bullseye view is for laying the device flat on a shelf, counter, or table top & the bubble snaps to the center and turns green when both angles reach zero. The tube view tracks roll on its own, so you can rest the long edge of the phone against a door, a frame, or a wall to confirm it is plumb.

Using it takes only a few steps:

  • Open the page on a phone or tablet, since most desktops and laptops have no motion sensors.
  • On iPhone or iPad, tap Enable sensors and choose Allow when iOS asks for permission to use motion data. The prompt only appears after a tap, which is why the button is there.
  • Lay the device on the surface you want to check and watch the live pitch and roll readings in degrees.
  • Place it on a surface you trust as flat and tap Calibrate to store that position as your zero, then use Reset to return to the raw sensor reading.

Bubble level app versus a browser tool

Many people search the app store for a bubble level app, or type "google bubble level" hoping for a quick answer in the search results. A downloaded app and a browser tool do the same core job, but a browser version asks for nothing more than a tap. There is no install, no account, and no storage taken up on your phone. If you only level a picture once in a while, a web bubble level tool is often the more convenient choice, and it works the same whether you are on Android or iOS.

Calibration matters more than most people expect. No surface is perfectly flat, and a phone case can add a slight slant of its own. Setting a custom zero on a reference surface removes that bias, which is the difference between a reading you can trust and a guess. Your calibration offset is saved in your browser, so it sticks between visits.

Everyday uses and accuracy

This is handy far beyond hanging frames. Use it to level shelves before you drill, to seat a washing machine or refrigerator so it does not rock, to check that a TV mount sits straight, or to even out table and chair legs. Whether you think of it as a small bubble level for quick household checks or a stand-in for a scope bubble level when squaring up a tripod, the same readings apply.

On accuracy, a calibrated phone is typically reliable to within a degree or so, which is plenty for shelves, pictures, furniture, and appliances. For precision engineering, masonry, or fine optical work, a dedicated physical level is still the right tool. Why does any of this matter? A surface that is even slightly off throws off everything stacked on it, and a frame that hangs a degree crooked is the kind of thing your eye notices every single day. A quick check with a bubble level saves you from redoing the job later.

Frequently asked questions

How do I use a bubble level on my phone?

Open this bubble level tool on your phone or tablet, tap Enable sensors, then lay the device flat on the surface you want to check. The bubble drifts off-center when the surface tilts and snaps to the middle, turning green, once it is level. For a vertical edge like a door or picture frame, stand the long button-free edge of the phone against it and watch the tube view instead.

How do I read a bubble level?

If the bubble sits centered between the marks, the surface is level. If it drifts to one side, that side is the high side, so the right side is higher when the bubble floats right and lower when it floats left. The same idea applies to plumb checks, just top and bottom instead of left and right. This tool also shows the exact tilt in degrees so you do not have to guess.

How accurate is a phone bubble level?

Once calibrated, a phone is typically reliable to within about half a degree to one degree, which is plenty for hanging pictures, leveling shelves and furniture, or checking if a floor slopes. Newer flagship phones tend to be the most accurate, while budget devices can drift a little more. For precision engineering, masonry, or fine optical work, a dedicated physical level is still the better tool.

How do I calibrate a phone bubble level?

Place the device on a surface you trust as flat, then tap Calibrate to store that position as your new zero. This cancels out any slant from your phone case or a slightly uneven sensor, which is the difference between a reading you can trust and a guess. The offset is saved in your browser so it sticks between visits, and Reset returns you to the raw sensor reading.

Why is the bubble off-center when my surface looks flat?

Two things usually cause this. First, the surface may genuinely be a touch out of level even though your eye cannot tell. Second, your phone case or the sensor itself may add a small bias, so rest the device on a surface you know is flat and tap Calibrate to zero it out. Removing a thick case and keeping your hands steady also helps the reading settle.

Does my phone have a built-in level?

Most likely yes. iPhones include a level inside the Measure app in the Utilities folder, and Android shows one when you search bubble level in Google. This browser-based bubble level tool does the same job on either platform without hunting for the right app, and you can add it to your home screen for next time.

Do I need to give permission to use the level on iPhone?

Yes. Since iOS 13, Safari hides motion and orientation data until you allow it, so tap Enable sensors and choose Allow when the prompt appears. The prompt only shows up right after you tap, which is why the button is there. If you accidentally declined, just tap the button again and approve it.

How do I level a picture frame, shelf, or appliance?

For a picture frame, rest the phone along its top edge and shift the frame until the bubble centers. For a shelf, lay the phone flat on it before you tighten the brackets. For a washer or fridge, set the phone on top and adjust the feet until it stops reading a tilt so the appliance does not rock. The live degree readout makes small corrections easy to dial in.

Can I level something without a real level?

Yes, that is exactly what this tool is for. Your phone already has the same tilt sensors a physical spirit level relies on, so a quick browser bubble level fills in when you do not have a real one in the drawer. For everyday jobs like frames, shelves, and furniture it is more than accurate enough once you calibrate it.

Is this bubble level free?

Yes, completely free with no app to download and no account. It is an online bubble level that runs entirely in your browser on Android and iOS, and no motion data ever leaves your device. Just open the page, tap to enable the sensors, and start leveling.

More tools

All tools →

Online Ruler

A calibrated ruler in cm and inches, right on your screen.

Printable Ruler

Download and print a precise ruler in inches and centimeters.

Online Protractor

A draggable protractor to measure angles in degrees.