Spin Axis

The tilt of the ball's spin axis as it flies through the air, measured in degrees from horizontal. A perfectly horizontal spin axis (0°) produces a straight ball flight with pure backspin; a tilted axis produces a curving ball flight.

A negative spin axis tilts the ball flight to the left (a draw or hook for right-handed players); a positive axis tilts it to the right (a fade or slice). Larger axis tilts produce more dramatic curve.

Spin axis is one of the harder metrics to measure accurately. Photometric launch monitors with multiple cameras (Foresight GC3, GCQuad, Uneekor EYE XO2) measure spin axis directly with high accuracy. Hybrid and radar units calculate it from other metrics, with varying accuracy.