Whiff rate measures how often hitters swing and miss against a pitcher’s offerings. It’s the per-swing version of swing-and-miss — distinct from SwStr%, which is per-pitch.

Whiff% is a leading indicator for strikeouts. A pitcher generating whiffs at a 30%+ rate is going to rack up Ks even if his command isn’t elite. Pitch-design discussions often center around whiff rate by pitch type — a slider with a 40% whiff rate is the kind of pitch that anchors a rotation.

Whiff% appears in Baseball Nut’s pitcher percentile Stuff section right after K% and K/9 because it’s the same skill viewed from a different denominator. K% measures the result; Whiff% measures the underlying mechanism.

What is a good Whiff%?

Whiff% is an underlying driver of K%, which is one of the three FIP components feeding NUT for pitchers. A pitcher generating a high whiff rate is producing the swing-and-miss results that lead to strikeouts.

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