Mueller Tactical Mildot 416X50mm *
Hawke Mildot and 1/2 Mil Dot Riflescopes

The Mil Dot reticle is primarily a range finding device that uses the optics of a riflescope and the known dimensions of a grid (the reticle) at unknown distances to estimate the sighted distance to a target. As a secondary function, the Mil Dots on the reticle can be set up as aiming points to compensate for holdover and wind drift. We'll address the range finding system first. Most Mil Dot scopes are set up to range find at 10X magnification. However, some scopes do it at whatever particular magnification the manufacturer has set the scope up for. Please note: Every Mil Dot scope has to be set at a specific magnification when you are using the reticle to estimate range. Be sure to set your scope for the proper magnification when ranging. 
MOA means Minutes of Angle... which is approximately equal to INCHES at 100 yards. Mils are the increments measured between the centers of the Mil Dots (ctc means center to center). 
100 yds  3.6" 200 yds  7.2" 300 yds 12" 400 yds  14.4" 500 yds  18" 
KISS  Keep It Simple Stupid...
The
idea is to read distance by simply looking thru your scope
while aiming. No complicated calculations... Just look and
know the distance. Explaining how it works makes it seem
more complicated than it is, so please bear with me as we go
thru the numbers.
Look at the "C" dimension in the chart and on the reticle above. 1 Mil at 100 yards is 3.6 inches or 1/10th of what it is at 1,000 yards (1/10th of 36 inches). At 200, 300, 400, etc... it is 2/10, 3/10, 4/10, etc. So, if you know the size in inches of a target, you can tell how far it is by the number of mildot increments it spans in your scope. Looking through the scope at a target 100 yards away, the distance between centers of two mil dots is 3.6 inches. If you figure the chest of a deer or antelope to be 18 inches high, at 100 yards the number of Mil dots it spans is 18 ÷ 3.6 = 5 Mil Dots. So, if you look at a deer through the scope and the chest spans 5 Mil Dots, that deer is 100 yards away. If the chest spans 2.5 Mil Dots, then the deer is 200 yards away... and so forth. See the charts at left. You should make your own chart for the dimensions of your target. This is the easiest way to estimate distances with Mil dots. 
Using Mil Dots as Aiming Points for Distance
Compensation  The easiest way is to compute the distances to
each aiming point with First Hit
Ballistic Reticle Software. For a few dollars you can let
your computer figure it all out in seconds... With extreme
accuracy.
Also, Hawke now offers their free
Ballistic
Reticle Calculator software (BRC) in a version that
calculates aiming points for the hybrid "1/2 Mil Dot" reticle. The distance between mil dots is 3.6 MOA at 10X magnification, right? That means it's 3.6 inches at 100 yards, 7.2 inches at 200 yards, and about 12 inches at 300 yards. That actually conforms pretty closely to some standard bullet trajectories ( 6.5mm BRM for example)... BUT, you can change the MOA between dots by changing the magnification (some scopes go higher than 10X). If you reduce the magnification the distance spanned between two dots increases. If you increase the magnification, the distance spanned between two dots decreases. So, the right magnification setting for each distance, you can have an exact mil dot aiming point. 