Free · No account required
Shot group size calculator
Enter shot-centre coordinates—or tap them onto a target—to calculate centre-to-centre extreme spread, mean radius and group-centre offset in millimetres.
| Shot | X (mm, right +) | Y (mm, up +) | Action |
|---|---|---|---|
| 1 | |||
| 2 | |||
| 3 | |||
| 4 | |||
| 5 |
Click or tap the plot to add a shot. The numbered coordinate fields provide the precise keyboard-accessible input.
Group results
- Extreme spread
- 5.42 mm
- Mean radius
- 2.17 mm
- Group centre
- X +0.28 · Y +0.12 mm
- Outside to outside
- 9.92 mm
Centre to centre
Average from group centre
Right/up are positive
Spread plus one projectile
How shot group size is calculated
Extreme spread is the largest centre-to-centre distance between any two shots. If you measure the outside edges of two clean pellet holes with calipers, subtract one pellet diameter to get the same centre-to-centre figure.
Mean radius first finds the average X/Y position—the group centre—then averages every shot's distance from that centre. It uses every shot, so one distant flyer does not dominate it as completely as extreme spread.
Group-centre offset says where the group sits relative to the target centre. A tight group with a consistent offset often points to a sight correction; a wide group around the centre is a different training problem.
What the result means on a 10 m target
| Target | 10-ring diameter | Pellet diameter |
|---|---|---|
| 10 m Air Rifle | 0.5 mm | 4.5 mm |
| 10 m Air Pistol | 11.5 mm | 4.5 mm |
Target dimensions: current ISSF Rule Book, General Technical Rules 6.3.4.3 and 6.3.4.6.
Skip the manual coordinates
TargetIQ detects shot positions from a complete paper-target photo, calculates these same group metrics automatically, and tracks them across sessions with scores, series and heatmaps.
Start scoring free →