To mark the ball, tap it once in the first frame; for the scale, choose either automatic (the ball’s real diameter) or manual (tap the two ends of a known distance and enter the metres). The scale is what converts pixel motion into real-world speed.
Mark the ball
Tap the ball in the first frame. For precision, zoom in and tap the ball’s centre rather than its edge. If you miss, tap again to correct.
Automatic scale
The app uses the standard ball diameter for your sport (football 22 cm, tennis 6.7 cm, volleyball 21 cm). It’s fast and good enough for most clips.
Manual scale (more precise)
Tap the two ends of a known distance that’s clearly visible in the frame, then enter the metres. Presets:
| Sport | Reference | Distance |
|---|---|---|
| Football | Goal width | 7.32 m |
| Football | Penalty spot | 11 m |
| Tennis | Service box | 6.40 m |
| Volleyball | Net (men) | 2.43 m |
| Volleyball | Net (women) | 2.24 m |
Manual calibration earns the 🧪 Scientist badge. Scale error maps directly onto speed — so pick the distance carefully.