K/9 Calculator

K/9 is strikeouts per nine innings — how many batters a pitcher would strike out over a full nine-inning game at their current rate. It scales raw strikeout totals so you can compare pitchers with different workloads.

Modern major-league starters often clear 8–9 K/9; elite arms push well into double digits. Lower levels and earlier eras posted lower averages, so always compare within the same context.

Equivalently, K/9 = strikeouts × 27 ÷ outs. Working in outs keeps 6.1 and 6.2 exact instead of treating them as decimals.

Use .1 and .2 for one or two outs in an unfinished inning. This calculator always converts to outs before dividing.

1. Total the pitcher's strikeouts.
2. Convert innings pitched to outs.
3. Multiply strikeouts by 27 and divide by outs (or multiply by 9 and divide by innings).
4. Round to two decimal places.

Worked example

90 strikeouts in 82.1 innings is 90 × 27 ÷ 247 ≈ 9.84 K/9. The same line as 90 × 9 ÷ 82.333… would require converting 82.1 to exact thirds first — outs avoid that mess.

K/9 is a rate per innings. Strikeout percentage (K%) is strikeouts per batter faced. A pitcher who works deep counts or faces more batters per inning can show different stories on the two scales. K/9 remains the everyday rate fans and box scores use.