Measure Size can do auto-segmentation of anything and tell you the width/height area of the object.
In the beginning, click the center "camera" icon to save the 3D image. Then press the "ruler" icon to find the object and measure size automatically! 
Or you can click the "dotted circle" icon to draw the range to be identified by hand.
Moreover, you can also click the "cube" icon to measure volume. (Please take the 3D image vertically on the table/ground, and click the table/ground on the screen when measuring volume).
It will display the width/height/area of the object. You can change the unit from cm to inches and the text color on the settings page.
You can also measure the distance from the camera/length/area of objects by clicking the screen to set the measurement range.

p.s. Measure Size uses LiDAR to detect the 3D position of objects. Please launch this application using iPhone 12 Pro or later / iPad Pro 2nd or later.
The object to be measured must be more than 20 cm away from the lens, and the distance from the center point of the screen will be displayed during measurement. If it is too close, less than 20 cm, it will be inaccurate!