Understanding & Using a Mil-Dot Reticle Scope (in Easy English)

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Understanding Mil-Dot Reticles, Formulas and calculationsDo you avoid mil-dot reticles because you don’t know how to use them?

Does magnification matter with a mil-dot scope?

And, no, Mil does not stand for military.

We promise not to throw out words like tangent, cotangents, fractions, and any other jargon that makes us sound fancy and leaves you confused.

We’ll go over everything you need to know about understanding mils for dummies, and how to effectively use them in the field in easy English.  Pinky promise.

via GIPHY

 

What is Mil-dot?

You may hear some people say that mil-dot or MRAD stands for military reticle.  However, mil is not an abbreviation for military.  Mil or MRAD is a shortened term for Milliradian, and yes, the military employs the use of mils in their optics.  So, what is a mil?

A milliradian is an angular measurement, and it is 1/1000th of a radian. A radian is a portion of a distance traveled around a circle. More specifically, a radian is the measurement of the arc created when two radius lines start at the center and end at the circumference of a circle. If you were to measure this arc for shooting purposes, you would measure it in radians.

Additionally, the length of the radian is also equal to the length of the radius, so the radian will always be the same size no matter how large the circle is. Therefore, a mil is a mil regardless of distance (we’ll get into this later).

Radians and Milliradian Demonstrated

With that said, there are a little over 6 radians in a circle. This means there are approximately 6,283 milliradians in a complete circle.

Most people are familiar with measuring this arc in degrees. You may have seen it said that 1 mil is the same as 1/60 degrees. However, the math ends up adding to 1 radian is approximately 57.296 degrees. Confused? Yeah, don’t think in terms of degrees. Instead, realize that radian and milliradians are another unit of angular measurement that is mostly seen in calculus and physics, but we use it for shooting too.

Using only a fraction of 1 radian for measuring means using very small angles that can drastically change bullet impact down range.

But, where does the “dot” in Mil-dot come in?

Many mil scopes employ a dot to indicate this milliradian measurement.  A dot does not equal 1 mil, but the space between it does.  You measure from the center of one dot to the center of the next dot and that equals 1 mil.

Mil-dot Reticle

 

Mil-dot VS Distance

How much does a mil measure in terms of distance?

A mil is a mil regardless of distance.  It is an angular measurement.  Distance is a linear measurement.  You can make a 1 mil adjustment on your scope, and it’s just a 1 mil adjustment.  But, if you want to measure what a 1 mil adjustment will do downrange at a known distance, you can calculate a linear size of where and how you want your bullet to move on that target.

Here are some numbers that reflect what size 1 Mil will be at known distances:

1 MIL SIZE CHART Distance (Yards) 1 Mil Size (Inches) Distance (Meters) 1 Mil Size (CM)
100 YARDS 3.6 INCH 100 METERS 10 CM
200 YARDS 7.2 INCH 200 METERS 20 CM
300 YARDS 10.8 INCH 300 METERS 30 CM
400 YARDS 14.4 INCH 400 METERS 40 CM
500 YARDS 18.0 INCH 500 METERS 50 CM
600 YARDS 21.6 INCH 600 METERS 60 CM
700 YARDS 25.2 INCH 700 METERS 70 CM
800 YARDS 28.8 INCH 800 METERS 80 CM
900 YARDS 32.4 INCH 900 METERS 90 CM
1000 YARDS 36.0 INCH 1000 METERS 100 CM/1M

 

And, so on….

You might want to write these numbers down. As you can see, since both the MIL system and the metric system are figured using powers of 10, the correlation between the two translates easily.

There is a definite advantage to learning the metric system. This makes it easy to be on the same page when you are working with a team that includes spotters and marksmen who are familiar with the metric system, and vice versa.

It’s now better to know both systems to effectively communicate linear distances. Adjustments and measurements using the scope reticle are, of course, made in MILS regardless of the unit of linear measurement. This means it’s always best to learn how to get a correction in mils by using your reticle without involving linear distance into the equation.

However, for sighting in and tracking scope consistency, we’ll take you through the math of when knowing the linear distance and using it to get a mil correction is helpful.

Since most shooters and hunters in the U.S. are already accustomed to inches, feet, and yards, we’re going to provide formulas for this system and the metric system, so you can use whichever you naturally find to be useful.

With that said, let’s give you the formulas to figure out what 1 mil translates to in size at any distance. You can print out the chart above or play around with the math until it’s burned into your brain.

 

FORMULA: CALCULATE 1 MIL SIZE AT ANY DISTANCE (INCHES)

(Distance x 3.6) / 100 = 1 mil size at that distance

For example: (525 yards x 3.6 inches) / 100 = 18.9 inches

1 mil at 525 yards = 18.9”


 

FORMULA: CALCULATE 1 MIL SIZE AT ANY DISTANCE (CM)

Distance / 10 = 1 mil size at that distance

For example: 1250 meters / 10 = 125 cm

1 mil at 1250 m = 125 cm


* Side Note: The 10 in this formula is a constant that allows a conversion from meters to cm with less math. So although it looks like the math is incorrect, it is actually just cutting out the need for a more complicated (distance / 1000) x 100 = 1 mil size in cm formula, since distance in meters / 10 = 1 mil size in cm yields the same result. Just know that when the constant 10 is used, the meter to cm conversion is done for you.

As you can see, the linear size of 1 mil increases the further the distance.

But, what do mil-dot reticles measure, and what do they do?

 

Understanding Mil Advantages

Why do you need mils?

Mil shouldn’t be confused with MOA (minutes of angle), although both are angular measurements.  For more on MOA and how they work, check out our thorough explanation here.

Mil can be used to holdover for bullet drop if weapon and ammunition ballistics are known.  It can also correct for wind drift if wind velocity and direction are also known.

With that said, mil-dot reticles are useful as a range finding tool.  You can use your reticle to estimate the size of a target at a known distance, or conversely, estimate the distance of a target of known size.

For example: You see a 10-inch/25.4 cm tall prairie dog in the distance of your crosshairs.  It’s taking up 1 mil on your reticle.  From the center dot to the first dot on the elevation crosshair, we know this is a space of 1 mil.  How far away is the prairie dog?

Calculating Distance to Prairie Dog 1 MIL

According to the 1 Mil Size Chart above, we can see that 10.8 inches is the same as 1 mil at 300 yards.  25.4 cm is about halfway between 200 and 300 meters, 1 mil would translate to approximately 250 meters.

The prairie dog is estimated to be about 300 yards/250 meters away – good enough estimate for recreational observation purposes only.  But, for shooters and hunters that .8-inch difference and approximate 250 m guess will translate to a miss when it comes to shooting the dog.  We must know exactly how far away the dog is to get dead-on.

Is there a math formula to get exact distances?  There’s quite a few.  You’ve been warned.

 

How to Use Mil Dots in a Scope

These days, hunters and shooters are carrying around a laser rangefinder to get the distance. Rarely will someone mil for a distance anymore. This practice is virtually dead among hunters.

But, like all optics, rangefinders can fail, and maybe when you need it most. If you know your formulas, then you won’t need to call it a day.

You can also consider using a mil-dot slide ruler. This is an analog calculator that has basically done the math and put it into the scale, so you don’t have to do it yourself. It can provide a distance for a target if you can determine the size based on how many mils it’s taking up in reticle. It can also provide a mil correction if you know your bullet drop. It doesn’t need batteries, and it takes the math out of the equation.

But, if you just like knowing how it can work together or acquiring the basic knowledge to do it yourself, let’s get into the math.

 

Measuring for Distance

FORMULA: TO CALCULATE YARDS TO TARGET

(Target size in inches x 27.778) / mil size = yards to target


FORMULA: TO CALCULATE METERS TO TARGET

 (Target size in cm x 10) / mil size = meters to target


 

Using the prairie dog example mentioned above, the prairie dog is 10 inches/25.4 cm tall, and it’s taking up 1 mil space on the crosshair from head to toe.  Using these formulas, we can calculate exactly how far away the dog is.

CALCULATING THE DISTANCE
YARDS 10" x 27.778 = 277.78 277.78 / 1 mil = 277.78 yards to prairie dog
METERS 25.4 cm x 10 = 254 254 / 1 mil = 254 meters to prairie dog

 

Remember, meters and yards are part of two different measuring systems.  While 254 meters looks starkly different to 277 yards – they’re the same distance.  Convert 254 meters to yards, and you have 277.

What if the prairie dog was taking up 2.5 mils on the crosshairs?  Change the mil size from 1 mil to 2.5 mils in the equations to look like this:

Calculating Distance to Prairie Dog 2.5 MIL

 

CALCULATING THE DISTANCE
YARDS 10" x 27.778 = 277.78 277.78 / 2.5 mil = 111.1 yards to prairie dog
METERS 25.4 cm x 10 = 254 254 / 2.5 mil = 101.6 meters to prairie dog

 

Side note:  27.778 is a constant.  There’s no need to get caught up in the nitty-gritty of why it’s 27.778.  Remember, it only works for figuring out the distance in yards.  It won’t work for meters.

 

Measuring for Size

Not many hunters are using their scope to measure size.  It’s also extremely difficult to train your eye to see to a 1/10th of a mil let alone stay steady enough to keep a still picture to measure it.  Outside of perhaps military applications, no one does this anymore.  Hunters memorize their kill zone on their intended target, they get a distance, holdover if needed, and they shoot within their parameters.

The number you really want to know when you’re in the field is the distance.

Most hunters should have a laser rangefinder.  Pull this out, and voila, you’ll know that bull is 272 yards/249 meters away.  But, what if you want to measure its antler span from left to right?  What if you want to know the formulas just because you’re interested?  Well, we’ll give it to you.

Via the reticle, we can see the antler spans 4 mils across the windage (horizontal crosshair) from point A to point B.

Calculating Antler Span Using Mils at known distances

 

Here’s the formula:

FORMULA: TO CALCULATE FOR SIZE IN INCHES

 (Distance in yards x mil size) / 27.778 = size (inches)


FORMULA: TO CALCULATE FOR SIZE IN CM

 (Distance in meters x mil size) / 10 = size (cm)


 

 
CALCULATING FOR SIZE
YARDS 272 x 4 = 1088 1088 / 27.778 = 39.2 inches
METERS 249 x 4 = 996 996 / 10 = 99.6 cm

 

There you have it.  The antler spans at 39.2 inches/99.6 cm from point A to point B.

 

How to Use Mil for Bullet Drop

To use a mil dot scope to get dead-on, you must know your rifle and your ammo ballistics which means knowing how far it drops over any given distance.

You can look up these ballistic stats online using an ammunition manufacturer’s website, or by filling out the needed specs on an online ballistics software program.

Let’s do an example: .270 Win with Federal Premium jacketed soft points 150 g zeroed for 100 yards.  0 mph wind.

I punch these numbers into Federal Premium’s ballistic calculator, or I can spend some extensive time at the range and get the drop numbers myself.  Here’s the amount of drop I can expect up to 500 yards.  The chart also tells me how much I must come up in mils to compensate for this bullet drop.

BULLET DROP & MILS TO COMPENSATE
100 YARDS/METERS BULLET DROP (INCHES): 0 MILS: 0 BULLET DROP (CM): 0 MILS: 0
200 YARDS/METERS BULLET DROP (INCHES): 4.2 MILS: 0.6 BULLET DROP (CM): 14 MILS: 0.8
300 YARDS/METERS BULLET DROP (INCHES): 15.7 MILS: 1.5 BULLET DROP (CM): 51.6 MILS: 1.9
400 YARDS/METERS BULLET DROP (INCHES): 37.6 MILS: 2.6 BULLET DROP (CM): 122.7 MILS: 3.4
500 YARDS/METERS BULLET DROP (INCHES): 73.0 MILS: 4.1 BULLET DROP (CM): 242.3 MILS: 5.3

 

Using an online ballistics calculator is a fast and convenient way to get the numbers.  But, for the sake of learning to calculate mil adjustments yourself, here’s the formula:

 

FORMULA: TO CALCULATE MIL ADJUSTMENTS

Bullet drop / 1 mil size for that distance = mils needed to adjust


 

For example: At 500 yards I take my 73 inches of drop and divide it by what I know 1 mil equals at 500 yards which is 18 inches.

73” / 18” = 4.06 mils that I need to adjust for bullet drop.

Round it, and I have 4.1 mils that confirms the numbers on the chart above.  However, there seems to be differing values when it comes to figuring out the mils using the metric system.

The chart above provides real ballistics using Federal Premium’s calculator.  They provided the bullet drop numbers in cm and the mils needed to adjust.  However, as you can see, the formula we just used won’t work to get the number of mils they suggested to adjust.

How did they calculate the mils?

via GIPHY

They took the bullet drop value in cm and converted it to inches first.  242.3 cm converted to inches is 95.4 inches.  Now, they used the formula outlined above.

95.4 / 18” = 5.3 mils (rounded up from 5.25).  Now our math is in line with this chart and their calculator.

But, other online ballistic calculators like Hornady uses the formula above.

For example: With an unspecified rifle and load for the sake of getting straight to the point, Hornady provides a 1271.7 cm drop at 500 meters and provides a 25.5 mil adjustment.  Let’s double check the formula:

1271.7 cm / 50 cm = 25.5 mils.  They didn’t do any converting to inches like what Federal Premium did.

However, using the same bullet weight, ballistic coefficient, and muzzle velocity in the Hornady calculator that I used in the Federal Premium calculator for .270 Win., it yielded almost exacting mil values with the cm to inch conversion. (*Trajectory/bullet drop was slightly different due to other data input I couldn’t cater for.)

Why is there a difference?

I don’t know the exact answer to why you would convert cm to inches first or when you would use the formula we provided.  I’m sure someone out there knows, but what I do know is rifle and ammo have a lot to do with it.  All rifles and ammo will behave differently.

Add to that terrain, weather, altitude, humidity, etc. and those values will change, sometimes only slightly.  On top of that, adrenaline and a sense of urgency to hit that trophy bull suddenly makes math almost impossible to comprehend in those moments.

What is the right ballistic calculator to use?

It’s the one that is the most appropriate.  Stick with manufacturer ones specific to your rifle and ammo.  You must reconfirm your values at the range however you came across it.  You might find the math and online apps are somewhat off to what you experience in reality at the range.

No matter how precise we try to be, there are multiple factors that will change the outcome.

 

What’s the point of all this?

  • Stick with the measuring system you know best!
  • Use the appropriate ballistic app/calculator.
  • Always reconfirm values at the range!

Now jot down your numbers onto your dope card for future reference.  But, how do all these numbers translate into making physical adjustments on the turret/clicks?

 

Making Adjustments with a Mil Dot Scope

1/10th or 0.1 mil scopes are all the rave today.  With turrets in 1/10th increments, you’ll be capable of making fine adjustments with 10 clicks per 1 mil.  Let’s look at an example using the numbers for the .270 Win. at 500 yards.

500 yards

73” bullet drop

Divide this by what I know 1 mil is at 500 yards which is 18″, so it looks like this:

73” / 18 = 4.06 mil

Round up: 4.1 mil to get on target.

I will need to turn the turret 4.1 mils.  This means making a total of 41 clicks.  Now, let’s see what my .270 chart should look like with confirmed mils to adjust.

DISTANCE / BULLET DROP / 1 MIL SIZE / MIL ADJUSTMENT / TURRET SETTING Distance Bullet drop 1 mil size Mil adjustment Turret Setting/(Total Clicks)
100 yards0 inches3.6 inches00 mil
200 yards4.2 inches7.2 inches0.60 mil - 6 clicks (6 clicks)
300 yards15.7 inches10.8 inches1.51 mil - 5 clicks (15 clicks)
400 yards37.6 inches14.4 inches2.62 mil - 6 clicks (26 clicks)
500 yards73 inches18 inches4.14 mil - 1 click (41 clicks)

 

You can fill out a dope card the same way for the metric system:

DISTANCE / BULLET DROP / 1 MIL SIZE / MIL ADJUSTMENT / TURRET SETTING Distance Bullet drop 1 mil size Mil adjustment Turret Setting/(Total Clicks)
100 meters 0 inches 10 cm 0 0 mil
200 meters 14 inches 20 cm 0.8 0 mil - 8 clicks (8 clicks)
300 meters 51.6 inches 30 cm 1.9 1 mil - 9 clicks (19 clicks)

 

Mil-Dot Reticles

The accuracy of your scope will depend on quality.  This will determine how consistent and repeatable your results will be.  But, most importantly, we need to talk about where your reticle sits in the erector tube.

Does your mil-dot scope have a second focal plane (SFP) or first focal plane (FFP) reticle?  Does it matter?  Absolutely!

If your scope is in the SFP, it means the reticle sits behind the magnifying lens assembly.  Why is this important?  It means you won’t be able to use the mil-dot reticle for range finding, size estimations, or for bullet drop compensation unless you’re in the manufacturer’s specified magnification setting which is usually max power.

Why?  1 mil will only truly equal 1 mil at max power where the manufacturer has designed the mil-dot reticle to be accurate.  It’s all about subtensions which you can read about in our Reticles Explained article.

SFP Reticle Demonstration

 

If your scope is in the FFP, it means the reticle sits in front of the magnifying lens assembly.  Because the reticle increases/decreases in size as you increase/decrease magnification, your mil-dot reticle will remain consistent to use across the entire power range.  You can use it to determine distance, size, and bullet drop at any time regardless of what magnification setting you’re in.

For more details on this, see our Subtension on FFP Reticles subsection.

FFP Reticle Demonstrated

 

Each scope will also employ a different type of mil-dot reticle.  You can have complex dots and lines that span the entire elevation and windage crosshairs to cover up to or more than 1000 yards.  Some may only provide a windage crosshair for wind drift requiring you to make elevation adjustments with a custom/specialized turret for bullet drop.

It’s important to read over specific manufacturer reticles to get an idea of how complex it is, or if it will be simple and fast to employ in the field.  The downside about mil reticles is they tend to get too busy to look at.

 

Last Words

We had a lot to say on the topic.  Most shooters, including myself, aren’t doing all these calculations behind the scope in the field.  Most shooters aren’t milling targets anymore.  So, what is a mil-dot scope for?

It’s just a different measuring system for getting dead-on.  It’s not inherently better than a MOA scope, and neither is MOA inherently better than mils.  Sure, you can measure size and distance with mils, but most just want to compensate for bullet drop and wind.  It’s no easy task to get out there and shoot at any distance and expect to get dead-on without knowing how your scope works and measures angles.  These angles translate to distance down range.

Get a lot of practice at the range to become familiar with how your rifle and bullets work, and how you can use your scope to make the best measuring judgements.  To start with, get a notebook and write this stuff down so you can burn it into your brain!

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Chris is a hunting enthusiast who is obsessed with optics & lives in a game-rich area. When most are in bed sleeping, you will find Chris hunched over a laptop researching the latest and greatest optic types, uses and specifications. Despite a love for writing and researching about optics, Chris prefers to keep out of the spotlight.