Calculate a pitcher’s K/9 (strikeouts per nine innings) from strikeouts and innings pitched, plus optional BB/9, K/BB and K%, or solve for strikeouts.
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K/9 Formula
K = total strikeouts and IP = decimal innings. Rearranged: IP = (K × 9) / (K/9) and K = (K/9 × IP) / 9. Inverse answers may be hypothetical or fractional if the supplied rate is rounded. The nearest recorded IP is shown separately and may imply a different rate.
What is K/9?
K/9 scales strikeouts to nine innings. Enter recorded innings as baseball IP: .1 means one out and .2 means two outs, not tenths of an inning. Strikeouts and recorded outs are distinct; an uncaught third strike can allow a batter to reach base.
K/9 vs. K%: K/9 uses innings; K% uses batters faced. For an illustration with two strikeouts and three outs per inning, two walks and no other baserunners produce 2/5 = 40% K%, while no baserunners produce 2/3 ≈ 66.7%. Both have 18 K/9. Extra batters and baserunner outs change the denominator, so the two rates are not interchangeable.
K/9 Benchmarks
The bands below are illustrative article comparisons, not universal ratings or calculator outputs. Compare pitchers within a specified league, season, role and workload. The retained era and player figures below are historical article snapshots, not current verified leaderboards.
| Rating | K/9 (Modern Era) |
|---|---|
| Elite | 10.0+ |
| Above Average | 8.5 – 10.0 |
| Average | 7.0 – 8.5 |
| Below Average | 5.5 – 7.0 |
| Poor | Below 5.5 |
MLB League Average K/9 by Era
| Period | League Avg K/9 |
|---|---|
| 2000-2009 | 6.6 |
| 2010-2019 | 7.9 |
| 2020-2024 | 8.8 |
| 2024 Season | 8.6 |
Historical Career Figures (Starters, original snapshot; min. 1,000 IP)
| Pitcher | Career K/9 |
|---|---|
| Blake Snell | 11.23 |
| Chris Sale | 11.09 |
| Robbie Ray | 11.07 |
| Jacob deGrom | 10.97 |
| Max Scherzer | 10.65 |
| Randy Johnson | 10.61 |
| Yu Darvish | 10.59 |
| Stephen Strasburg | 10.55 |
| Gerrit Cole | 10.37 |
| Kerry Wood | 10.32 |
| Pedro Martinez | 10.04 |
Single-Season Records
| Pitcher | Year | K/9 |
|---|---|---|
| Shane Bieber | 2020 | 14.20 |
| Gerrit Cole | 2019 | 13.82 |
| Jacob deGrom | 2020 | 13.76 |
| Spencer Strider | 2023 | 13.55 |
| Randy Johnson | 2001 | 13.41 |
| Pedro Martinez | 1999 | 13.20 |
Historical Relief Pitcher Figures (original snapshot; min. 300 IP)
| Pitcher | Career K/9 |
|---|---|
| Aroldis Chapman | 14.88 |
| Craig Kimbrel | 14.66 |
The original career figures above are retained as historical references. Active players’ totals change, and these tables are not live rankings. Role and workload affect comparisons; the calculator itself computes the supplied numbers without assigning a performance rating.
