Ruler

Use your Android device as a ruler, with all the simplicity and ease of use of a typical ruler.
There are 2 scales to satisfy both people who prefer the Imperial system and people who prefer the metric system.

It is simple, accurate and user-friendly. (No calibration required)

Note : Get a ruler along with several other useful utility tools such as scientific calculator, calendar, unit converter, flashlight, stopwatch, timer, etc. all in one place with Mobile Utilities :
https://play.google.com/store/apps/details?id=andromart.mobileutilities