K/9
Strikeouts per 9 innings.
What K/9 means
Volume rate. League average for starters ~9, dominant relievers can sit above 12. K% is the more stable rate.
How K/9 is calculated
K/9 = K × 9 / IP
What counts as a good K/9
Higher is better — roughly 7 is poor, 8.5 average, 10 good, and 11.5 or better elite.
Also written
k_per_9 · so9