Home How To`s How To Calculate MOA @ Different Magnification Levels

How To Calculate MOA @ Different Magnification Levels


sniper rifle magnification MOA

Most shooters, even those moderately familiar with a rifle understand that a certain level of math is necessary for precision shooting. Most shooters will know this math exists but will never actually need it for their hooting. Those looking to shoot with precision and to put rounds in as small a group as possible or those looking to make accurate shots at long range need to be keenly aware of a variety of different factors. This includes everything like: measuring wind, distance, and even things like humidity, and the effects of the earth rotating. All this is involved in making precision grade shots.

So, What Is MOA?

The first thing you need to understand is MOA, which is an acronym for minutes of angle. Minute of angle is an angular measurement and is 1/60th of a degree. MOA is so handy because 1 MOA spreads at right around an inch at 100 yards, and the measurement is consistent for every hundred yards. Since most rifle ranges are spelled out in hundreds, MOA is very handy to understand and know. Truth to be told, 1 MOA is not an exact inch though, it’s 1.047.

How Magnification Affects MOA?

Most precision shooting and most long range shooting is done with an optic. Optics also traditionally have magnification, which can affect how you utilize your minute of angle.

Certain scopes will change the value of your MOA as the magnification is amplified. There are different focal planes scopes to operate on:

  • the first or front focal plane.
  • the second focal plane.

changes in rifle scope reticle between first and second focal plane

With the first focal plane there is no effect to your MOA regardless of magnification. First focal plane scopes are usually quite expensive, and uncommon, although they are growing in popularity.

For example, check the (price) difference between Bushnell AR Optics 1-4×24 front focal plane vs second focal plane version.

With the second focal plane you’ll be forced to compensate and understand how magnification can change MOA size. Typically MOA is correct at the highest magnification setting of the optic. So an optic with a 10 power magnification has a 1 MOA at one hundred yards when the magnification setting is 10x.

Calculating MOA At Other Magnification Levels

Most scope manuals will give you an idea of the scope MOA at one magnification or another. Let’s say we opened up our scope manual and we see that the reticle is 10 MOA at 18 power. When you reduce the magnification level to 9 the MOA would change to 5 MOA. You’ll need to do a simple transition to calculate the MOA in accordance with the magnification. So 18 power equals 10 moa, and 9 power equals 5 moa, and that means 4.5 power equals 2.5 MOA.

Another method is the shoot and see. This is the funner, but obviously more expensive method. This is certainly a timely method and requires a lot of ammunition and note taking.

Calculating Bullet Drop

Something else important is calculating bullet drop on an optic when you do not have a specific bullet drop compensator built into your rifle. This an easy method to use MOA and a mil dot system to calculate bullet drop at different ranges and magnifications. You will need a data book, and be apt and patient for taking notes. You’ll have to take notes for every range and every magnification.

This means if you want a complete and total list you’ll have to make tack marks, large enough to see at a good distance. The tac marks should be 3.6 inches apart. At hundred yards you’ll notice 1 mil falls between the tack marks. At one hundred yards 3.4377 MOA equals a literal hair under 3.6 inches when multiplied by the actual MOA at 100 yard,(1.047), so we round up just a hair.

So on a mil dot scope 1 mil equals 3.6 inches at 100 yards. So at one hundred yards you get 3.6 inches per mil, at two hundred yard you 7.2, and at three hundred yards you get 10.8 inches. So you know at 300 yards 1 mil represents 10.8 inches of bullet drop.

Here is more in-dept guide on using the mil-dot reticle for measuring distance.

Can`t Get Past Mathematics

Precision shooting is not always easy to accomplish. To be a precision shooter you must of course master the rifle, but you’ll also need to use a bit of math, and hope for a little luck. This is just the border of the amount of mathematics than can go into shooting, but it is important know.