What is Minute of Angle (MOA)?

MOA is the abbreviation of the term Minute Of Angle. MOA is commonly used to describe the relative accuracy of a firearm. MOA is also less commonly described as Minute of Arc or Arcminute.

Calculating MOA is usually undertaken in empirical measurements ie inches and yards.

Fundamentally, MOA is 1/60th of one degree. A full circle is divided into 360 degrees and each degree is divided into 60 minutes. Thus, there are 21,600 minutes in a full circle (360 x 60 = 21,600).

Therefore, to calculate MOA, imagine a very large circle with a 100 yard radius (distance from the circle centre to the edge of the circle). This circle would also have a circumference (the full perimeter distance of the circle) of approximately 628.32 yards or 22,619 inches.  By dividing the circumference (22,619 inches) by the number of minutes in a full circle (21,600 inches) gives a value of about 1.047 inches (22,619 / 21600 = 1.047). Similarly, the size of a bullet's impact point would change by 2.094 inches at 200 yards (1.047 x 2) and change by 3.141 inches at 300 yards (1.047 x 3) and so on.

So, if you calculate 1/60th of a degree when firing a rifle at a target 100 yards away, the measurement between the two lines of the angle that radiate from your shooting position to the target 100yards away is 1.047 inches or approximately 1 inch.

A major concept that most target shooters or hunters need to understand is that for every firearm and ammunition combination employed there will be a specific and individual MOA value associated with that combination. We are considering purely MOA in this discussion, however it should be noted that there are factors or variables that impact on the MOA. Such obvious factors are the variances attributed to the expertise of an individual operator of the firearm.

In evaluating MOA potential of a particular rifle and ammunition combination, it needs to be highlighted that precision and accuracy do not mean the same thing.  That is, rifle precision is a measure of how close a bullet will hit at the same point it had before. Where, rifle accuracy is hitting the aiming point. When combing precision and accuracy, where the point of aim coincides with accuracy we call this MOA Performance.

Therefore MOA is a concept that provides the shooter a reference point for evaluating Performance of any combination of firearm and ammunition. 

By understanding the MOA Performance concept it is also possible to provide an understanding at what ranges a shooter could conceivably hit targets, particularly at long distances. In deed, if all things are made equal, it also provides feed back as to the ability of the operator.