COMMON QUESTIONS
Online bubble level FAQ
Answers about phone support, bubble level calibration, accuracy, offline use and slope measurements.
Can I measure slope percentage or set a target angle?
Choose Slope / angle with a long phone edge along the slope. It shows degrees, percentage grade and rise:run. Open Target angle for a custom value or 0°, 45° and 90° presets. Positive means the phone’s top end is higher. Set zero makes these values relative to your reference; Reset zero restores the sensor reference.
Does the level work offline?
Tap Save offline while connected and wait for Saved offline. Reopen the same address in the same browser without internet. The tool and guides are cached locally; supported motion sensors and permission are still required. Your browser can remove cached files, particularly in private browsing or after clearing site data.
Does this work on a laptop?
Most laptops do not provide the motion sensor this tool needs. Open this page on a phone with a supported browser.
What does “Set zero” do?
It treats the phone’s current steady position as your reference. The following angles show the difference from that position, not absolute level. Use Reset zero to return to the sensor’s original reference.
Is this as accurate as a physical spirit level?
Accuracy depends on your phone, browser, case and placement. We have not certified a numerical accuracy for this tool. Use a physical level when precision or safety matters.
Is this bubble level free to use?
Yes. The level runs in your browser with no download, account or payment. Readings are calculated on your phone and are not sent to a server.
Which phones and browsers does it support?
It works on Android and iPhone browsers that expose the motion sensor over HTTPS. iPhones ask for motion access the first time you start. If the level does not start, the setup guide lists fixes.
What does the Hold button do?
Hold freezes the current steady reading so it stays on screen. That way you can lift the phone to inspect the surface, or note the angles, without the display changing while you move.
Can I check a wall or a vertical surface?
Yes. Choose Edge / wall and hold the screen facing you with a straight phone edge against the wall or frame. The angle shows the difference from the nearest horizontal or vertical reference. Follow the rotation guidance. Use Flat surface when the phone is lying screen-up.
What does “near level” mean?
The result uses an on-screen guide of 0.5° in each direction to decide when to say a surface is near level. That guide is a display threshold, not a measurement of your phone’s accuracy.
What happens when I change modes or rotate my screen?
The tool clears Set zero and any held reading because the measurement axes have changed. Place the phone again and wait for a steady reading before setting a new reference.
Can I copy a reading or get a sound when it is level?
Copy reading copies a steady snapshot, including the mode and whether Set zero was used. Hold freezes it first if you want to lift the phone. Sound is off by default; turn it on to hear a short tone when a steady reading enters the near-level guide.
Still stuck?
The setup guide covers placement, motion permission and calibration in detail. Check the Contact page for current support availability. When reporting an issue, include your phone model and what you saw.