Your iPhone now contains a “Measure” app that acts as a high-tech tape measure. Just launch the app, point your camera at something, and it will measure dimensions of objects in the real world.

This is one of the many new features in the iOS 12 update. It uses augmented reality—specifically, Apple’s ARKit technology. Apps like this already existed in the App Store, but now one comes with the iPhone.

Launch the “Measure” app to get started. You’ll see it somewhere on your home screen, and you can always swipe down on the home screen and search for “Measure” to find it.

You’ll be prompted to move your iPhone around to calibrate the Measure app. You don’t need to do anything fancy—just move the iPhone around until it says you’re ready to begin.

When the app is ready, point your iPhone at the thing you want to measure, and you’ll see a dot in a circle. Tap the plus sign button to add the starting point for measuring. That point will remain anchored to the object in the real world, even as you move your phone around.

Now, just move your phone. It will measure the distance between the point you placed and whatever is under the dot at the center of your screen.

If the point you want to measure is too far away, you’ll be prompted to choose a closer object. Move closer to the object you want to measure, if possible. You won’t be able to measure properly if you’re too close, either.

Tap the “+” button again to place the second point and anchor it on the screen. The Measure app will draw a line between the two points.

You can continue this process to measure multiple distances and have them on screen all at once.

Tap the back arrow button at the top of the screen to undo your last action, or tap “Clear” to remove every point you’ve placed on the screen.

Your iPhone will automatically prompt you to measure some objects, too. Just move your phone so the object is positioned under the dot at the center of your screen, and you may see a prompt to add a shape around the object.

Tap the “+” button to draw lines around the object and measure its dimensions automatically.

This app also contains a “Level” feature. Just tap the “Level” button on the toolbar at the bottom, and the phone will measure the angle at which┬áit’s oriented. Place your iPhone on a surface to see whether it’s flat—or exactly how many degrees it’s off by if it isn’t.

When the phone is placed on a level surface, the screen will say 0 degrees and will turn green.

We found the Measure app pretty accurate. However, we encourage you to double-check with a physical tape measure or ruler if you need precise measurements. The app won’t always get a perfect measurement in every scenario. We wouldn’t rely on Measure as the final word in a carpentry project any time soon.

RELATED: What’s New in iOS 12, Arriving Today, September 17