This simple yet effective universal propeller protractor, a must have tool for any pilots garage. 

This can be used to determine pitch, or to set the pitch on a variable pitch propeller.

This tool combined with your smart phone will make a very accurate protractor. It is designed to accept almost any smart phone, and can be used for much more than propellers. 

There are two prop cutouts designed for a variety of propeller sizes, but all 4 sides can also be used for calibration, or measuring.