You're cheating.

Well, only sorta kinda, because you're only working at 100 yards and because one minute of angle is usually rounded to 1" at 100 yards so it all works out the same. That's not exact but it's so close that the rounding error doesn't matter.

So, riddle me this.... how much would you need to adjust if you were shooting at, say, 150 yards? Or 200 yards? That's where MOA comes in.

Let's say your drop at 150 yards is 16.5 inches down from your HV zero at 50 yards. How many clicks do you need to adjust to get on target? Your 1/4" clicks at 100 yards aren't 1/4" at 150 yards, eh? So you can't multiply 16.5 inches by four to get the number of clicks needed to get on target. How many would it take? Time's up! (42 clicks)

If you are working in MOA, however, it's easy math since your 1/4" at 100 yards clicks are actually (more or less) 1/4 MOA clicks. So, in our example, let's say we know our trajectory in MOA instead of inches. We know that at 100 yards we have a drop of 4.5 MOA and that at 150 yards it is 10.4 MOA and at 200 yards it is 17.6 MOA. So our click count at 100 yards is 4.5*4=18 clicks and at 150 yards is 10.4*4= just over 41 clicks and at 200 yards is 17.6*4=just over 70 clicks.

MOA -- minute of arc (shooters say minute of angle for whatever reason) -- is an angular measure, not a linear measure. Draw an angle. Put four hash marks across to connect the two legs at different points -- one about halfway to represent 100 yards, one at the end to represent 200 yards, then marks in between to represent 50 yards and 150 yards.

The angle doesn't change so the distance between the two lines when expressed as an angle (MOA) doesn't change. What does change is the distance between the lines expressed as a linear measure... if our angle is one MOA wide it is one inch wide at 100 yards but only 1/2" wide at 50 yards, two inches wide at 200 yards, etc.

Since the value expressed in inches will change with distance you have to convert the 1/4 MOA clicks of your knobs to inches at that distance. You have to do math to first convert those inches to MOA at that distance so you know how many clicks to count (since they really represent ~1/4 MOA and not 1/4 inch). If you're only working at 100 yards it doesn't matter since MOA and inches are more or less equal at 100 yards... but only at 100 yards. If you're shooting at longer distances it's really easier to skip all the converting and just track your trajectory in MOA.

Let me know if that only confused you more and I'll try a different... er... angle.