Smash factor is calculated by dividing ball speed by club speed at impact. It's a measure of how efficiently energy transferred from the club to the ball.
A perfectly centered strike with a driver typically produces a smash factor around 1.50. Iron strikes typically fall in the 1.30–1.40 range due to the lower launch and higher spin that irons are designed to produce.
Why it matters
Smash factor isolates the quality of contact from raw clubhead speed. A golfer swinging 80 mph who consistently centers the face will out-distance someone swinging 90 mph who mishits the ball — because their smash factor is higher.
For practice, smash factor is one of the most useful single metrics for tracking improvement, because it goes up as your strike pattern tightens.
Smash factor on a launch monitor
Any launch monitor that measures both ball speed and club speed reports smash factor directly. Units that only measure ball speed (and estimate club speed) will report a smash factor too — but it's calculated, not directly measured, so it's less reliable as a diagnostic tool.