Free, no advertising and no need of permissions to install! You can move the slider to get a better measure. The "laser" that comes from the slider will tell you the exact length in centimeters. Just put the small thing on the screen, with one end at the 0cm position and move the slider to the other end.
This application was originally developed by Patán Libre and it is related to the Tools category. The most recent update of Ruler cm was launched on Sep 10, 2014 and the app was downloaded by over 100K users. On Google Play, this application was rated 3.2 by its users.