Smash factor tops out near 1.5

Ball speed rarely exceeds about 1.5× clubhead speed, even on a perfect driver strike.

Why it works

Smash factor (ball speed ÷ clubhead speed) is capped by the physics of the club-ball collision — 1.5 sits close to the legal-driver ceiling. Shorter, more lofted clubs run lower, around 1.1–1.4, since more energy goes into spin instead of ball speed.

Do it exactly

Estimate with the rule, then check it against the calculator that models it properly.

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