How to measure a person’s height using an iPhone camera
1. Open the Measure app on your iPhone.
2. Place the iPhone so that the entire person you want to measure is visible on the screen.
3. After that, the height measurement is displayed just below the line that appears at the top of the person's head (or hair, or hat).
Then, tap on the Take Picture button to capture a picture of the measurement.
4. Tap on the screenshot available in the lower-left corner to save the image.
5. Select Save to Files or Save to Photos after tapping on the Done button.