oneminuteofangle

One minute of angle (MOA) is a unit of angular measurement equal to 1/60 of a degree. In radians it is about 0.000290888, and in milliradians about 0.291 mrad. Because small angles approximate linearly, 1 MOA corresponds to a roughly constant lateral shift at a given range.

At distance D, 1 MOA subtends a lateral displacement of about D × 0.000290888 radians, so it is roughly 1.047 inches at 100 yards, 2.094 inches at 200 yards, and 10.47 inches at 1000 yards. This makes MOA convenient for expressing aiming errors, group sizes, and sight adjustments.

MOA is widely used in shooting sports and optics to describe accuracy, windage and elevation adjustments, and reticle subtensions. Many rifle scopes offer adjustments per click measured in MOA (for example, 1/4 MOA or 1/2 MOA per click). A common rule is that a 1 MOA adjustment moves the point of impact by about 0.26 inches at 100 yards. The metric alternative is the milliradian (mil), where 1 MIL is 1/1000 rad and 1 MOA is about 0.291 mrad, roughly 3.437 MOA per MIL.

The concept derives from the subdivision of degrees into arcminutes and arcseconds and remains standard in firearms, hunting, and some surveying instruments for describing precision and adjustments.