Want to know if you are shooting sub-MOA? MOA Calc is a simple MOA calculator to calculate the MOA of a grouping of shots on a target.
For the uninitiated, Minute Of Angle (aka. Minute Of Arc) is often used to measure the accuracy of rifles. Often rifle manufacturers will advertise their rifles are guaranteed as being sub 1 MOA. In addition, most modern rifle scopes are adjustable in half (1/2), quarter (1/4) or eighth (1/8) MOA increments (aka. Clicks).
The app has both metric and imperial MOA calculators.