Width · AR ruler

A ruler app that measures with the camera

A phone screen is only about 15 cm tall, so a ruler drawn on it stops being useful the moment the thing you are measuring is bigger than the phone. The camera has no such limit.

Free: 3 width measurements a day · Premium: unlimited

Download on the App Store
The Width tool measuring a picture frame on a wall at 50 cm

Screen ruler or camera ruler?

There are two kinds of ruler app. The first draws a ruler on the display. It is exact for small things you can lay on the glass, like a screw, a coin or a ring, but it ends where the screen ends.

The second kind, which is what Measuring Tape does, uses the camera and Apple's ARKit to find real surfaces in the room. You place a start point and an end point in the world, and the app works out the distance between them. That lets you measure a doorway, a desk or a wall from where you stand.

For anything longer than your phone, the camera ruler is the one you want.

How it works in the app

  1. 1

    Open Width and move the phone slowly until the badge says AR Calibrated.

  2. 2

    Put the center mark on one edge of the object and tap the shutter.

  3. 3

    Move sideways to the other edge and tap again. The width stays on screen until you reset.

  • Meters, inches or feet

    Pick metric, inches or feet in Settings. The app starts in the unit your country uses.

  • Flashlight

    Turn on the torch in dark corners so the camera can find the surface.

  • Save the result

    Take a screenshot of the measurement straight to your photo library.

Questions

Is there a ruler on the iPhone?

iPhones come with Apple's Measure app, which uses the camera like this one. There is no ruler drawn on the screen built in. Measuring Tape adds height, area and a bubble level in the same place.

How accurate is an AR ruler?

Close, not millimeter-exact. Expect a small error that grows with distance. Good light, a textured surface and moving the phone slowly at the start all help. Check once with a real tape before you cut anything.

Can I measure something small, like a screw?

AR works best on things from about 10 cm up. For very small parts a printed ruler or calipers will be more reliable. Our guide on reading a ruler shows how to read the small marks.