# What is a Milliradian?

A Milliradian is a measurement of angle. Oh how I wish I could stop there…

A Milliradian is 1000th of a Radian. Mille being from the Latin meaning of one thousand.

# So what is a Radian?

Being completely honest, I have read a lot on this subject and even reading the descriptions of other people multiple times it is difficult to comprehend. What I believe is the simplest way of describing it is as follows.

1 Radian is an angular measurement of a circle where the curved “arc” of the measure is equal to the radius of the circle.

A radian is the pie-chart version of an equilateral triangle, where all sides are equal in length, albeit one of them (the radian arc) is curved.

Lets see if a picture helps.

# How Many Radians in a Circle?

*Remember at school when you’d complain to the teacher about never needing to use trigonometry in real life, well, take it back.*

We need to work out the circumference of a circle using 2*π*r then divide it by r.

2*π*r = 2*π
* r

2 * *π* = 2 * 3.14159

Number of Radians in a circle = **6.283185**

Regardless of the size of the radius, there will only ever be this number of radians as the angle stays the same.

# How does this pertain to shooting?

Now we understand what a radian is, we can use a portion of it to apply to shooting. Like Degrees and MOA, the unit of measure is too big to be useful for shooting, so we use 1000th of a Radian for use with shooting.

Just to reiterate, one Mil is 1000th of a radian.

Mil (Or Milliradians) is an SI Unit and often considered the metric equivalent to MOA, due to the way it works hand-in-hand with the metric system.

Sights generally come with Mil adjustments, or MOA adjustments (aside from a few Russian offerings which don’t come in either).

# How will knowing what a Mil is help me hit my target?

Using a standardised measurement of angle such as Mil gives us a relationship for adjusting our sights based on bullet trajectory, or bullet impact.

If we were to draw a triangle that had the 2 longest sides 100 metres long (*since Mil works beautifully with metric I will work examples in metres rather than yards*) joined at one end and 1 mil apart all the way along, at the opposite end to the join they would be 10 cm apart. Therefore we can deduce that at 100 metres 1 Mil is 10 cm.

Since the Radius is equivalent to the Radian, and in this case the Radius is 100m. Therefore 1000th of the arc/radius is the angle of measurement. So we divide 100m by 1000 giving us 1/10th of a metre, or 10cm.

10cm at 100 metres however is not enough accuracy resolution to win competitions where the NRA bull at 100m is only 5.5cm.

Sights therefore come in 2 major offerings where Mil is concerned. Either 1/10th Mil, or the super fine, 1/20th Mil clicks.

To use a similar scenario as the one used on the Understanding MOA post:

How can we use this information to our advantage?

We know that if we are hitting 5 cm to the left of target and 2.5cm high at 100 metres, we need to move half a Mil to the right and ¼ Mil down to get on target. Since sights in Mil usually come in 1/10 Mil clicks or 1/20 Mil clicks. We can calculate how many clicks will get us on target. (5 right, 2 down or 10 right and 5 down respectively) This does highlight the resolution issue with 1/10th Mil sights where the lowest resolution they will go is 1 click = 1cm at 100m therefore to correct our scenario we would either have to be .5cm above or .5cm below our target, this is of course corrected with a 1/20th click sights, where the lowest resolution at 100m would be .5cm per click.

This may not seem like a lot, especially as the discrepancy is less than the diameter of the bullet for a lot of applications, however it is worthy of notice for long range shooters…

# What about at longer range?

As shown in the image above the arc gets bigger in a linear fashion to the radius, which means the further you shoot the larger a Mil is. Thankfully in Mil it is easily formulated. At 1000 metres, 1 Mil = 1 Metre. [r(distance)/1000].

At 1000 metres, 1 click will be:

1/10th : 10cm

1/20th : 5cm

At 600 metres, 1 click will be

1/10th : 6cm

1/20th : 3cm

# What about Mil under 100 metres?

As above, since it’s an easily worked out formula of distance / 1000 to work out the millirad, it doesn’t matter what the distance, it will always be a (fairly) simple calculation. At 50 metres (50 / 1000) 1 Mil will be 0.05m or 5 cm. At 25 metres 1 mil will be (25 / 1000) 0.025m or 2.5cm. Divide these numbers again by 10 for 1/10th click sights and you have your click values. 0.5cm clicks or 5mm clicks at 50 metres. 0.25cm or 2.5mm clicks at 25 metres.

# Further Reading…

What about the relationship between MOA and Mil?

We can find out the direct relationship between MOA and Mil, since they are both linear angular measurements using commonalities;

1 MOA is **1/60th** of a degree. In decimal; **0.01666** recurring

1 radian is **1/6.283185** of a circle (360 degrees).

360/**6.283185** = **57.29578** Degrees

Therefore **1 Radian** is roughly **57.3** degrees.

One Millirad (divide by 1000) is **0.0573** degrees.

**Direct Relationship:** **1 Mil is 3.438 MOA**.

3rd March 2016 at 9:23 pm

Yes ! I’ve finally got it – Thanks