Strikeouts per nine innings pitched

${\displaystyle K/9IP=9\cdot {\frac {K}{IP}}}$

In baseball statistics, strikeouts per nine innings pitched (abbreviated K/9, SO/9, or SO/9IP) is the mean of strikeouts (or Ks) by a pitcher per nine innings pitched. It is determined by multiplying the number of strikeouts by nine, and dividing by the number of innings pitched.