How to measure group size and convert it to MOA
Calipers, a little subtraction and one conversion will give you group numbers that you can compare between loads and distances.
Published November 2, 2026
Center to center
The standard measure of a group is the distance between the centers of the two shots farthest apart. You can’t easily see the centers, so measure the outside edges of those two holes and subtract one bullet diameter.
With a .308 bullet and an outside measurement of 0.81 in:
0.81 - 0.308 = 0.50 in center to center
Converting to MOA
A minute of angle (MOA) is an angle, so the same MOA covers more inches the farther away the target is. One MOA is about 1.047 in at 100 yards, and it scales directly with distance.
| Distance | 1 MOA covers |
|---|---|
| 100 yd | 1.05 in |
| 200 yd | 2.09 in |
| 300 yd | 3.14 in |
To convert, divide the group by the inches per MOA at that distance. A 0.50 in group at 100 yards is 0.50 / 1.047 = 0.48 MOA. The same 0.50 in group at 200 yards would be 0.24 MOA.
From group to clicks
The group’s center tells you where to move the scope, and its size doesn’t. Measure from the point of aim to the center of the group, then divide by what one click moves at that distance.
On a scope with 1/4 MOA clicks, one click moves about 0.26 in at 100 yards. If the group’s center is 1 in low, that’s 1 / 0.26 = about 4 clicks up. Check your scope’s markings, since some use different click values or use milliradians (mrad) instead of MOA.
How many shots to count
Group size depends on how many shots you fire. A group can only get bigger as you add shots, so three-shot groups tend to look better than five-shot groups from the same rifle and load. Two things follow:
- Only compare groups with the same number of shots.
- Don’t crown a winner from one group. Shoot several and compare them, because one small group can be luck.
Center to center only uses the two widest shots and ignores the rest. Mean radius, the average distance of every shot from the group’s center, uses all of them and is steadier with fewer shots. It’s harder to measure by hand, but software can work it out from marked shots.
Measuring from a photo
In AmmoLoader, you can photograph your target on range day, line up an on-screen target over it and mark the shots. The app works out group size, spread and the sight change in clicks, and keeps them with the load and rifle. To put those numbers to use, see how to test your handloads against factory ammunition.
The figures here are made-up examples for the arithmetic, not prices or load data. AmmoLoader doesn't recommend charge weights. Always follow published load data from the powder and bullet makers.