Free tool
MOA Group Size Calculator
Convert a group measured at any distance to MOA, IPHY and mils.
How to measure group size
Group size is normally measured center to center: the distance between the centers of the two shots that are farthest apart. The easy way is to measure from the outside edge of one hole to the outside edge of the other, then subtract one bullet diameter. Enter that edge-to-edge number with your bullet diameter above (in the same unit), and the calculator does the subtraction for you. This holds even when the holes overlap: if every shot went through one ragged hole, measure across its widest point and subtract one diameter. A perfectly round single hole is a group of zero.
MOA, IPHY and mils
- MOA (minute of angle) is 1/60 of a degree. It covers about 1.047 in at 100 yards, or 2.91 cm at 100 meters, and grows in proportion to distance.
- IPHY (inches per hundred yards), sometimes called “shooter's MOA”, rounds that to exactly 1 inch at 100 yards. It's simpler to work out in your head but about 4.5% smaller than true MOA, so a group of 1 IPHY is 0.955 MOA. Many scopes are marked in true MOA, so it's worth knowing which one you mean.
- Mils (milliradians, MRAD) are 1/1000 of the distance: 10 cm at 100 meters, or 3.6 in at 100 yards. Scopes with mil turrets usually adjust in 0.1 mil clicks.
All three measure an angle rather than a size, which is why they let you compare a pistol group at 7 yards with a rifle group at 300.
How much is 1 MOA at common distances
| Distance | 1 MOA | 1 mil |
|---|---|---|
| 7 yd | 0.073 in | 0.25 in |
| 10 yd | 0.105 in | 0.36 in |
| 15 yd | 0.157 in | 0.54 in |
| 25 yd | 0.262 in | 0.90 in |
| 50 yd | 0.524 in | 1.80 in |
| 100 yd | 1.047 in | 3.60 in |
| 200 yd | 2.094 in | 7.20 in |
| 300 yd | 3.141 in | 10.80 in |
| 500 yd | 5.236 in | 18.00 in |
| 1,000 yd | 10.47 in | 36.00 in |
| 100 m | 2.91 cm | 10.0 cm |
| 300 m | 8.73 cm | 30.0 cm |
The formula
A group of size s at distance d, both in the same unit, spans an angle of 2 × atan(s / 2d). Multiply that angle in radians by 3,437.75 for MOA, or by 1,000 for mils. At normal shooting distances the angle is small enough that s / d gives the same answer to several decimal places. For IPHY, scale the group to 100 yards: inches × 100 ÷ yards.
Group size or CEP?
MOA tells you how big a group is at any distance, but group size itself has limits: it's set by your two or three outermost shots, ignores all the others, and grows as you fire more of them. For tracking progress over many sessions, CEP — the radius containing half your shots — holds up better. See CEP vs Group Size for why, with a worked example.
Skip the ruler
Target Detect measures groups for you. Photograph the target and on-device machine learning finds every shot, then reports group size, CEP and their MOA equivalents for the distance you logged — turn on Show Grouping in MOA in Settings to see groups in MOA. See Reading a Session Analysis, or get Target Detect on the App Store — $4.99, one-time purchase.