The short version: MOA and MRAD are two units for measuring the same thing — angle. Neither is more accurate than the other. The only genuine mistake is buying a scope whose reticle is in one unit and whose turrets are in the other, because then every correction requires a conversion under time pressure.
MOA
A minute of angle is one sixtieth of a degree. It subtends 1.047 inches at 100 yards, which everyone rounds to one inch — so 1 MOA is about 1 inch at 100 yards, 2 inches at 200, 5 inches at 500. Most MOA scopes adjust in quarter-MOA clicks, so one click moves the point of impact about a quarter inch at 100 yards.
MRAD
A milliradian is one thousandth of a radian. It subtends 3.6 inches at 100 yards, or precisely 10 centimeters at 100 meters — which is why it is elegant in metric. Most MRAD scopes adjust in 0.1 mrad clicks, so one click moves about 0.36 inches at 100 yards.
MOA is finer per click, MRAD is faster to communicate and to do arithmetic with. Both are more precise than any of us shoot.
Using them in practice
The correction arithmetic
Your group is 3 inches low and 2 inches right at 100 yards.
In MOA, 3 inches at 100 yards is about 3 MOA. At quarter-MOA clicks that is 12 clicks up. 2 inches right is 2 MOA, so 8 clicks left.
In MRAD, 3 inches at 100 yards is 3 ÷ 3.6 = 0.83 mrad. At 0.1 mrad clicks that is 8 clicks up. 2 inches is 0.56 mrad, so about 6 clicks left.
Same correction, different arithmetic. Neither is harder once you have done it twice.
The distance multiplier
Both scale linearly with distance, which is the entire point of an angular unit. 1 MOA is 1 inch at 100 yards and 4 inches at 400. 1 mrad is 3.6 inches at 100 yards and 14.4 at 400. A correction dialed at one distance is correct in angle at every distance.
Matching reticle to turrets
This is the only part that genuinely matters. If your reticle has MRAD hash marks and your turrets click in MOA, then every time you spot a miss with the reticle you must convert before you dial. That conversion happens in the field, under time pressure, and it is exactly when arithmetic goes wrong. Buy matched.
Which to choose
- MOA if you think in inches and yards, shoot with people who do, or hunt in the US where that is the common language.
- MRAD if you shoot in a metric context, participate in precision-rifle competition where MRAD dominates, or prefer the cleaner arithmetic.
- Whichever your shooting partners use. Being able to say "come up 0.4" and have someone dial it correctly is worth more than either unit's theoretical advantage.
Red dots use MOA too
A 2 MOA dot covers about 2 inches at 100 yards; a 6 MOA dot covers about 6. That is the same arithmetic, applied to the dot's apparent size rather than to a correction — and it is the whole basis of the dot-size decision.
How these were picked
I haven't handled these. Here's what I did instead.
Everyone in this category says they tested twenty of these. I haven't tested any, and I say so. What I do instead: read the manufacturer's manual and published specification, compile the numbers that decide the purchase, do the arithmetic in the open, check the live price, and name one product to skip. The scores above are judgments from that research against a published rubric — they are not measurements I took, because I do not have a lab and I am not going to pretend otherwise.
