Best Measuring Apps for Android

Measuring apps bundle four different tools that happen to share an icon, and they are not equally trustworthy. One of them is genuinely accurate enough to hang a shelf with. Another should be treated as an estimate you check with a tape. Knowing which is which is the whole of this guide.

Spirit level. The most reliable by a distance. It reads the accelerometer and orientation sensors, which are precise and stable. Calibrated on a flat surface, it is accurate to a fraction of a degree, which is more than enough for shelves, picture frames and a curtain rail.

Protractor and angle finder. Same sensors, same reliability, as long as you can hold the phone flush against the surface.

AR distance and area measurement. Impressive and approximate. It builds a model of the room from the camera and motion tracking, and small errors accumulate over distance. Fine for deciding whether a sofa will fit. Not fine for ordering a worktop.

On screen ruler. The weakest. It depends on the app knowing your exact screen dimensions, and it can only measure something smaller than the phone. A novelty rather than a tool.

Every phone sits slightly off true, and a case makes it worse. Calibration takes twenty seconds and is the difference between a usable level and a confident wrong answer.

• Find a surface you know is flat. A kitchen worktop or a glass table is usually better than a floor.
• Lay the phone down, run the app calibration, then turn it 180 degrees and check it still reads level. If it does not, the surface was not flat, so try another.
• Take a thick case off first, or calibrate with it on and leave it on. What matters is that the conditions match.
• Recalibrate after a drop, and after changing case.

AR measurement fails in predictable ways, and most of them are fixable.

• Move the phone slowly across the surface first, until the app shows it has found a plane. Rushing this is the main cause of nonsense results.
• Give it texture and light. A plain white wall in dim light gives the camera nothing to track, and accuracy collapses.
• Measure the same span twice from different starting points. If the two answers differ by more than a couple of centimetres, do not trust either.
• Keep spans short. Error accumulates, so a room measured in one sweep is worse than the same room measured wall by wall.

AR measurement also needs a device with the right platform support. Older and cheaper phones may show the feature but produce poor results, or not offer it at all.

This category has an unusually high proportion of low quality apps, because "measure" is an easy thing to promise and a hard thing to verify. Before installing, check the last updated date, the review count rather than just the score, and the permission list.

The permission list is the strongest signal. A measuring app legitimately needs camera for AR modes and nothing else. The sensors it uses for levelling need no permission at all. An app that wants location, contacts, phone state or storage access is asking for things the job does not require, and that is reason enough to pick another.

All in one toolboxes that combine level, ruler, protractor and distance are the sensible default: one app, one set of permissions, and the tools you actually need are the accurate ones anyway.

Almost all of these are free and funded by advertising. A small one time purchase, typically the price of a coffee, removes the ads and sometimes unlocks extra units or saved measurements.

That purchase is worth it for one specific reason: ads in a measuring app tend to appear as full screen interruptions exactly when you are holding a phone against a wall with your other hand full. Paying to remove them buys usability, not features.

Be honest about the limits. For anything you will cut, order or install to a fixed size, use a tape measure. The phone is for deciding, checking and levelling, not for committing.

Specifically: do not use AR measurement for worktops, blinds, flooring quantities or anything where being two centimetres out means buying it twice. Use it to narrow down, then confirm with something physical.