Strikeout rate
also: K% · strikeout percentage · BB% · walk rate
Strikeouts as a share of plate appearances; walk rate is the same for walks.
Formula
K% = SO / PA; BB% = BB / PAPer plate appearance rather than per at-bat, so a hitter who walks a lot is not flattered. Strikeout and walk rates stabilise faster than batting average, which is why they lead most early-season reads of a hitter or a pitcher.
For a pitcher the same rates, measured against the batters faced, are the cleanest read of how much of the outcome he controls: strikeouts and walks do not depend on the defence behind him.
The common mistake
A low strikeout rate is not always good: contact that is weak contact makes outs too. Read it with OPS.
Where to get it
Related
Strikeout rate from the API
500 free credits on signup, no card. REST or MCP.
Get a free key