What is Minute of Angle - MOA?

MOA is a mathmatical concept that most firearm scopes incorporate. Minute of Angle (MOA) is critical to sighting in your scope. MOA mathematical concepts were used to develop the AccuScope scope sighting reference tool.

The only MOA information needed to use AccuScope is your scope's MOA number. AccuScope determines the number of adjustment dial increments or "clicks" to rotate your scope's elevation or windage adjustment dial to accurately sight in your scope at multiple shooting distances.

Each click of the scope turret is usually 1/4 or 1/2 MOA change and on some scopes 1/8 MOA. Normally, shooters refer to these adjustments as a change of a fraction of an inch at 100 yards rather than the true value of MOA for which they are supposedly calibrated to.

Calculating Angle of Arc

The angle of an arc is expressed in number of degrees. There are 360 degrees of arc to a full circle. Each degree consists of 60 minutes of arc. The distance covered by the measure of arc is relative to the circumference (total distance around the circle) it is contained within. Knowing the radius (distance to center of circle) circumference is easily calculated by using the constant pi .

The ratio (represented by pi ) of circumference is constant to diameter (radius x 2) regardless of circle size. The precise value of pi is so far unknown to man but is normally resolved to 3.1416 or 3.141 for our purposes.

Suppose a circle with a 6 inch radius. Circumference can be calculated as: circumference = (radius x 2) x pi circumference = (6 x 2) x 3.1416 circumference = 12 x 3.1416 circumference = 37.6992 inches The distance covered by 1 degree of angle (37.6992 / 360 or, circumference divided by 360 degrees) is 0.1047 inch at 6 inches from center of circle. And, 1 minute of angle represents (0.1047 / 60 or, 1 degree divided by 60 minutes) 0.001745 inch at 6 inches from center of circle.

Knowing what MOA represents allows us to calculate its value to any distance. Six inches (the radius of the above example) is 1/600th of 100 yards: (100 yards x 36 inches) / 6 inches = 600 Therefore, the value of MOA at 100 yards is 1.047 inches (0.001745 x 600 = 1.047) At 50 yards 1/2 the 100 yard value; 70% @ 70 yards; twice @ 200 yards; 6 times @ 600 yards; and so on. So, the difference between thinking in inches as opposed to MOA is 10.47 inch @ 1000 yards.

Who has time to figure this out when you should be shooting?

We transform this complicated concept into a simple, easy to use tool. In short, AccuScope is "MOA made simple". Although MOA mathematical concepts were used to develop AccuScope, the only MOA information you need to use AccuScope is your scope's MOA number. AccuScope comes in two versions. The first version is designed for 1/4 MOA and 1/2 MOA scopes - these scopes are most common. The second version is for 1/8 MOA scopes - these scopes are becoming more and more popular due to their increased precision.

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