On Glass: MOA vs MIL

If you’ve spent any time around long-range shooters, you’ve probably been bombarded with the terms MIL and MOA. If you’re brave, you may have asked what those terms mean and been bludgeoned by a long-winded explanation about inches and centimeters interspersed with opinions about things like wind number and speed drop, leaving you more confused than before.

Not for nothing are long-range shooters considered the calculator watch-wearing, rubrics cube-solving, nerds of the shooting world.

What follows is a guide to MOA and MIL that can be understood by people who don’t want to get another academic degree to hit targets far away.

What even is a MOA or MIL?

Both MOA and MIL (or MRAD) are forms of measuring an angle. Have you ever described turning completely around as a 180-degree turn? If so, you’re using the same sort of measurement as a MIL or a MOA.

On a super technical level, a MOA (minute of angle) is 1/60th of a degree, and a MIL or MRAD (milliradian) is 1/1000th of a radian, but you don’t need to know that. All you need to understand is that neither is a measurement of distance, but instead a measurement of angle.

Therefore, they only correspond to inches and millimeters at specific distances. One MOA will respond to roughly 1 inch at 100 yards (technically 1.047 for the pocket protector crowd), 2” at 200 yards, 3” at 300 yards, and so on. One MIL corresponds to 3.6 inches at 100 yards, 2.6 at 200 yards, and so on.

How they are used

Either unit of measurement can be used for adjusting your impact down range, creating a dope card (a chart of how much to adjust for different ranges), and holding off target for wind. You can also use either, in tandem with your scopes reticle and some math, for determining the range of a target of a known size without a laser range finder.

MOA is also commonly used to measure a gun's mechanical accuracy. If a gun shoots a 10-round group of a 2" size at 100 yards, that gun is referred to as a 2MOA gun. Assuming the shooter executes the fundamentals and makes a good wind call, we can extrapolate that such a gun could shoot a 4" group at 200 yards, 6" group at 300 yards, etc, until the cartridge reaches the limit of its effective range. 

Converting between the two

It is possible to convert numbers between the two forms of measurement. To convert MIL to MOA you technically need to multiply by 3.43775. But with numbers like that, we are DEEPLY into the glasses-wearing territory of chess club champions.

3.5 is a much easier-to-remember conversion number that will be good enough for most applications. Want to convert 2 MILS to MOA? Multiply by 3.5 to get 7 MOA. Want to go back to MIL? Divide by 3.5.

Example: we want to know how much 4 MIL of adjustment will move our impact at 500 yards. 4 MILs multiplied by 3.5 gives us 14 MOA. 14 MOA is (roughly) 14” at 100 yards times 4 (for the 400 yards) gives us 70” for 500 yards

The Reality is FAR Simpler

That’s the theory behind the two ways of measuring angles. In reality, virtually all modern scopes have matching dials and reticles, meaning whatever unit of measurement one clicks on your scope’s dial is, it will correspond to the marks on your scopes reticle. This means that most of the time, you’ll just adjust off what you see in the reticle, rather than worrying about math or conversions. Thank God.

Most modern scopes have synchronized reticles and turrets. This means that if your scope turrets adjust your point of impact in MOA, then your reticle will be set up to measure what you’re seeing in MOA. (Historical note: this was not always the case – scopes from 20 years ago routinely had MIL reticles and MOA turrets, forcing the shooter to run conversion math constantly). Thus when you select a scope, you should get a scope that is set up in the system of measurement (MOA or MIL) that you prefer. 

Should I buy an MOA scope or a MIL scope?

If you’re buying a modern optic, you'll have the option to choose a scope set up in MOA or MIL (also called MRAD) units, unless it’s a BDC scope (ballistic drop calculator – a fancy way of describing different lines at different distances for approximately where your bullet will land at that distance). Which should you pick?

Pick MOA If

•  You are part of a team or group where everyone uses MOA scopes. Converting between measurements mid-conversation or engagement is a hassle you and your buddies don’t need. If everyone around you is using MOA, use MOA so you can see and discuss the same wind calls, holdovers, and adjustments.

• If you already have a bunch of other MOA scopes and that’s how all your data is currently set up. If you like MOA and use it already, there’s no reason to add a headache by having some MIL scopes and some MOA. But chances are, if you already are in the MOA system, you aren’t reading this article right now.

Everyone else should pick MIL scopes

The reason for this is most of the scopes in the long-range community are MIL and because of that, most shooters speak the language of MIL. When you’re learning and improving, it will be a lot easier to ask questions and get advice (such as wind call suggestions) if you are using MIL data.

There are also some fun tricks and cheats you can use, like gun number and speed drop, available if your scope is a MIL scope.

MIL hacks – Gun number

Gun number is a way of dramatically simplifying wind calls while using a MIL scope. Once you find your gun number by using a ballistic computer or ballistics app on your phone, you can use that and the wind speed to quickly determine how many MILs you should hold in a certain direction to hit your target.

For instance, my Tikka is a 6mph gun, meaning a 6mph full value (90 degree) wind will require .1 MIL of adjustment per 100 yards. So if I have a target at 500 yards with a 6mph left-to-right wind, I have to hold .6 MIL’s to the left to hit the target. If the wind is 9mph in the above scenario, then I would hold .9 mils, 1.2 for 12 mph, etc.

Gun number is an incredibly useful shorthand hack that I almost every time I'm shooting past 300 yards.

MIL hacks – Speed drop

Speed drop is a similar concept for elevation (hold overs) instead of windage (left to right). You determine your gun’s speed drop when you find the range of distances where 1 MIL of elevation adjustment works for 100 yards of distance. There are a few different ways to use and set up your gun for speed drop, and that’s beyond the scope of this article, but it is yet another tool that’s available to you if you select a MIL scope.

I personally don’t use speed drop, but some shooters who are better than I swear by it, so it’s a good tool to have available if you want to use it.

Common Objection: I want an MOA scope because I think in inches

This is the most common objection new shooters use when getting an MOA scope. I made the mistake of getting a MOA scope when I was starting because of this very line of reasoning. It was also a mistake. I sold the scope midway through my first full year of competing and bought a MIL scope at a loss.

Remember, outside of your initial zeroing, when you’re adjusting your point of aim through a scope, you’re adjusting based on the reticle. If I told you to aim 18 inches to the left, that wouldn’t be helpful, because without a tape measure down range (and I’ve never seen a target conveniently paired with a tape measure), you wouldn’t know what 18” is. But if I told you to hold left .6, you would go to that hash mark on your reticle and send the shot.

If you have a MIL scope, you can still use MOA to think about things like how accurate your overall system is with certain ammo types, but all of your adjustments will be based on turret adjustments and reticle holdovers, not measuring out distances on a ruler.

Final checks

• MOA and MIL are units of measuring angles, not distance

• 3.5 is the simple conversion factor to swap between them

• If you’re on a team where everyone has MOA scopes, get a MOA scope

• Everyone else should get a MIL scope