In baseball statistics, strikeouts per 9 innings pitched (K/9IP or K/9) is the mean of strikeouts, (or K's) 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.
The all-time leader in this statistic is active San Francisco Giants pitcher, Randy Johnson (10.67 SO/9). The only two other players who are have averaged over 10 are both active, Kerry Wood (10.385) and Pedro Martínez (10.081). Note that the previous statement is based on innings pitched minimums that apply mostly to starting pitchers. For relievers, using 300 career innings pitched or 200 appearances as the minimum. For instance, the record holder is Brad Lidge (RP) who is the all-time leader in strikeouts per nine innings (12.98 K/9) among pitchers with at least 200 appearances in their career.