MOA - Minute of Angle explained
360° : 360 = 1°
1° : 60 (Minute) = 1 MOA
The definition of minute of arc, or minute of angle, is a unit of angular measurement equal to 1/60th of a degree. This results in a very precise adjustability for scopes with MOA subdivision. Rifle scopes are available with adjustment turrets in 1 MOA, 1/2 MOA, 1/4 MOA and the particularly fine 1/8 MOA subdivision [adjustment per click]. For example, 1/4 MOA scopes have an adjustment of 7.3 mm per click at 100 m and 1/8 MOA scopes have an adjustment of 3.6 mm per click at 100 m.