If you own an iPhone 12 Pro or iPhone 12 Pro Max, or a later iPhone "Pro" model, your device boasts a neat feature that allows you to measure the height of someone using just the Measure app and the iPhone's camera and LiDAR Scanner. This article and video shows you how.

The capability comes courtesy of the LiDAR scanner that's exclusive to Apple's Pro line of smartphones as well as iPad Pro models released in 2020 and later. LiDAR is intended for enhanced augmented reality experiences, but the measuring feature is just one unexpected yet highly practical advantage of the scanner.

Launch the Measure app on your iPhone or iPad.
Locate the person whose height you want to measure within the camera's viewfinder. They can be either seated or standing – just make sure their whole body is visible from head to toe within the frame.
Wait a moment, and a line should appear at the top of the person's head with their height measurement.
To take a photo of the measurement, tap the shutter button located immediately right of the central plus (+) button.
To save the photo, tap the screenshot in the bottom-left corner of the screen, tap Done, then choose Save to Photos or Save to Files.
To take the measurement again, simply turn your iPhone away for a moment to reset the height.

That's all there is to it. Note that you can switch the measurement between imperial and metric by going to Settings -> Measure, and selecting your preference under "Measure Units."