180 strikeouts and 48 walks is a 3.75 K/BB
K/BB tells you how many strikeouts a pitcher records for every walk he issues. MLB's official glossary defines it as total strikeouts divided by total walks. With 180 strikeouts and 48 walks, 180 ÷ 48 = 3.75, which means 3.75 strikeouts for each walk. Innings pitched and batters faced are not part of the formula.
That 3.75 is 1.26 above the 2026 MLB regular-season average of 2.49, but it is not an elite number by itself: 21 of the 46 MLB pitchers who threw enough innings to qualify were higher still, and 33 of them beat the league average. The league average also includes every pitcher who fell short of the qualifying mark, so a starter is better judged against the qualified group. That is why the calculator above shows both. A pitcher who walked 48 batters at the average MLB ratio would have struck out about 120. On the slope chart, walks per nine innings run left to right and strikeouts per nine run bottom to top, so K/BB is the slope of the line from the corner to a pitcher's dot.
Why look at K/BB
A strikeout is an out the defense never has to make, and a walk is a runner the defense could not stop. The MLB glossary describes the walk as a measure of a pitcher's command, and FanGraphs points out that strikeouts and walks are results a pitcher largely controls himself, which makes them useful for judging his skill. K/BB puts the two in one number. Typical uses:
- Checking command in a strikeout pitcher: a pitcher who strikes out many but also walks many keeps putting runners on. 200 strikeouts against 100 walks is a K/BB of 2.00, close to the league average.
- Tracking change between seasons: put last season and this season side by side in the comparison line. The arrow on the slope chart shows whether the ratio rose because of more strikeouts or fewer walks.
- Comparing pitchers across leagues: MLB, NPB and KBO have different walk and strikeout environments. The same 3.00 is 0.51 above the MLB average but only 0.23 above the NPB average.
- Reading a number in a broadcast or article: when someone says a pitcher is "at 5 to 1", you can check whether that means strikeouts per walk, which is what K/BB is, or the reverse ratio used for hitters.
How to use the calculator
- Enter strikeouts and walks from the same stretch of games in the "Strikeouts K" and "Walks BB" boxes. Do not count hit batters as walks.
- Choose the league to compare with: MLB, NPB or KBO. The verdict sentence and the dots on the slope chart switch to that league's 2026 regular-season values.
- If you know the innings, write them as the box score does, like 165.1. A dot appears on the slope chart and you get K/9 and BB/9. Adding batters faced also gives you K% − BB%.
- To compare with last season or another pitcher, enter strikeouts, walks and optionally innings under "Comparison line". You get the change, the percentage change and an arrow on the slope chart.
- Press "Same difference line" on the slope chart to switch the guide lines to parallels of equal strikeouts minus walks per nine. Two real pitchers with similar K/BB but a very different margin are marked.
How it is calculated
- K/BB: strikeouts ÷ walks, rounded to two decimals for display. With 0 walks and at least one strikeout it shows ∞. With 0 of both it is not calculated.
- K/9 and BB/9: innings are turned into outs first (whole innings × 3 + the digit after the point), then strikeouts or walks × 27 ÷ outs. Both are divided by the same innings, so K/9 ÷ BB/9 equals K/BB.
- K% − BB%: (strikeouts − walks) ÷ batters faced, shown as a percentage with one decimal.
- League average: add up every pitcher's strikeouts and walks in that league, then divide. It is not a simple average of individual K/BB figures.
- Comparison line: the change is the difference between the two displayed values (two decimals). The percentage change uses the unrounded values.
The fewer the walks, the more one walk moves K/BB. The "With one walk more or fewer" row of the calculator shows that range.
| Line | Strikeouts | Walks | K/BB | With one walk more or fewer |
|---|---|---|---|---|
| Full season as a starter | 180 | 48 | 3.75 | 3.67 to 3.83 |
| Last season | 150 | 50 | 3.00 | 2.94 to 3.06 |
| 19.2 innings in relief | 24 | 2 | 12.00 | 8.00 to 24.00 |
| Short line, no walks | 15 | 0 | ∞ | - |
League average K/BB (2025 and 2026 regular seasons)
K/BB fell in MLB and KBO in 2026. Strikeouts were about the same, but walks went up. In MLB, walks rose from 15,379 to 16,337 while strikeouts moved only from 40,645 to 40,700, so the average dropped from 2.64 to 2.49. NPB walked more too, but strikeouts rose even more, and its ratio edged up from 2.74 to 2.77. The same 3.00 reads differently depending on the season you hold it against, so compare with the average from the same season.
| League | Season | Strikeouts | Walks | K/BB | K/9 | BB/9 | K% − BB% |
|---|---|---|---|---|---|---|---|
| MLB | 2026 | 40,700 | 16,337 | 2.49 | 8.50 | 3.41 | 13.3% |
| MLB | 2025 | 40,645 | 15,379 | 2.64 | 8.49 | 3.21 | 13.8% |
| NPB | 2026 | 13,430 | 4,841 | 2.77 | 7.91 | 2.85 | 13.4% |
| NPB | 2025 | 12,475 | 4,559 | 2.74 | 7.29 | 2.67 | 12.3% |
| KBO | 2026 | 11,054 | 5,319 | 2.08 | 7.80 | 3.75 | 10.1% |
| KBO | 2025 | 11,024 | 5,123 | 2.15 | 7.77 | 3.61 | 10.5% |
The KBO team pitching tables do not list batters faced, so the plate appearances in the team batting tables (56,732 in 2026) stand in for them. Across a whole league the plate appearances batters take and the batters pitchers face are the same thing.
K/BB of qualified pitchers
The innings qualifier is 1.0 inning per team game (MLB Rule 9.22). Pitchers who reach it are mostly starters who work deep into games, so their K/BB runs above the league average. In MLB in 2026, 33 of 46 qualified pitchers were above 2.49. So what is a good K/BB? Neither the MLB glossary nor FanGraphs gives a grading scale. A starter is better judged by where he sits among qualified pitchers than by whether he beats the average.
| League (2026) | Qualifier | Pitchers | Highest | Median | Lowest | Above league average |
|---|---|---|---|---|---|---|
| MLB | 162 IP | 46 | 6.45 (Chris Sale) | 3.19 | 1.61 (Merrill Kelly) | 33 |
| NPB | 143 IP | 22 | 8.82 (Haruto Takahashi) | 4.15 | 2.31 (Allen Kuri) | 18 |
| KBO | 144 IP | 18 | 8.32 (Ko Young Pyo) | 3.24 | 2.06 (Natsuki Toda) | 17 |
Chris Sale (Atlanta) struck out 200 and walked 31. Pitchers with very few walks see their K/BB jump like this, so among the leaders one or two walks can change the order.
Same ratio, different pitcher
The weakness of K/BB is that it is a division. A pitcher who strikes out 20% and walks 10% of batters and one who strikes out 10% and walks 5% both have a K/BB of exactly 2.0. Per 100 batters, the first nets 10 extra strikeouts and the second only 5. Tom Tango tested this in 2010 using pitchers from 1993 to 2009 who faced at least 1,500 batters.
| Group of pitchers | Pitchers | K% | BB% | K/BB | Runs per 9 |
|---|---|---|---|---|---|
| BB 11% or more, K 21% or more | 20 | 24.2% | 12.1% | 2.0 | 4.26 |
| BB under 7%, K under 14% | 20 | 12.1% | 5.9% | about 2.0 | 4.94 |
| BB under 7%, K − BB 10 to 14% | 24 | 18.0% | 5.7% | over 3 | 4.14 |
The first two groups have the same K/BB, yet their runs allowed differ by almost 0.7 (4.94 − 4.26 = 0.68). The first and third groups differ in K/BB (2.0 against more than 3), but their strikeout-minus-walk margins are close (12.1 and 12.3 points) and so are their runs allowed. Tango's conclusion was to look at the difference, not the ratio, and FanGraphs likewise says the bigger the gap between strikeout rate and walk rate, the more effective the pitcher.
The 2026 MLB season has its own example. Jesús Luzardo (Philadelphia) struck out 221 and walked 52 for a K/BB of 4.25. Nick Martinez (Tampa Bay) struck out 109 and walked 26 for 4.19. The ratios are almost the same, but their K% − BB% is 23.2% against 11.5%, about double. The calculator's "Command vs power" example has the same shape. A command pitcher with 120 strikeouts and 24 walks (K/BB 5.00) trails a power pitcher with 220 strikeouts and 88 walks (2.50) in strikeouts minus walks per nine, 5.08 against 6.79. If you know batters faced, read K% − BB% next to K/BB.
Common mistakes
- Counting hit batters as walks: the BB in K/BB is the walk alone. A hit by pitch is recorded separately in the MLB glossary, so adding it lowers the ratio. An intentional walk does count as a walk.
- Averaging individual K/BB figures: the simple average of the 18 qualified KBO pitchers in 2026 is 3.71, but adding up all their strikeouts and walks and dividing gives 3.36. The same gap shows in MLB (3.47 against 3.24) and NPB (4.23 against 3.90), because a few pitchers with very few walks pull the simple average up.
- Judging a line with only a few walks: 24 strikeouts and 2 walks is 12.00, but one more walk makes it 8.00.
- Treating a tier chart as official: cutoffs like "3.00 or better is excellent, under 2.00 is poor" appear in neither the MLB glossary nor the FanGraphs article. Compare with the league average of the same season.
- Comparing with another season's average: the KBO average fell from 2.15 in 2025 to 2.08 in 2026. Holding a 2026 line against the 2025 average makes it look worse than it is.
- Reading innings .1 as 0.1: it does not change K/BB, but K/9 and BB/9 are off. 165.1 innings is 165⅓ innings, or 496 outs.
Limits
- K/BB says nothing about home runs or what happens on balls in play. To connect it to runs allowed, read it alongside FIP and WHIP.
- FanGraphs says relievers strike out about 3 percentage points more of the batters they face than starters and walk about 1 point more. Qualified pitchers are almost all starters, so a reliever's line set against them can be misleading.
- It is a raw value with no adjustment for league, park or season. Across leagues it is better to measure distance from each league's average, as this calculator does.
- The KBO record room's qualified table has no batters faced, so the slope chart is drawn in per-nine rates instead of K% and BB%. The same-difference line is also strikeouts minus walks per nine.
- League averages and qualified-pitcher lists are final regular-season numbers as checked on 2026-10-21. The postseason is not included.
- What you enter is not sent to a server. The calculation runs inside this browser, and values go into the address only when you press "Copy link" or edit a value.
As of The formula and explanations were checked on 2026-10-22 against the MLB glossary, the FanGraphs Library and The Book Blog. League averages and qualified pitchers were calculated on 2026-10-21 from the 2026 regular-season records of the official KBO and NPB record rooms and MLB (Stats API).
Sources
- 01MLB Glossary — Strikeout-to-walk Ratio (K/BB)Definition: strikeouts per walk, total strikeouts ÷ total walks
- 02MLB Glossary — Walk (BB)Four balls put the batter on first; a measure of the pitcher's command and the hitter's eye
- 03MLB Glossary — Hit-by-pitch (HBP)A hit by pitch is recorded separately from a walk
- 04MLB Glossary — Rate Stats QualifiersRule 9.22: 1.0 inning per team game for pitchers
- 05FanGraphs Library — Strikeout and Walk RatesPiper Slowinski (2010-02-19): K% and BB% formulas, the bigger the gap between the two rates the more effective, no adjustments, relievers about 3 points higher in K% and 1 point in BB%
- 06The Book Blog — Strikeout, walks: ratio or differential?Tom Tango (2010-03-23): runs per nine of 4.26 and 4.94 for two groups at K/BB 2.0, conclusion to use the difference
- 07KBO Record Room — Team records (pitching)2026 regular season, 10 teams: 11,054 strikeouts, 5,319 walks, 12,760⅔ innings; 2025 on the same table: 11,024, 5,123, 12,773⅔ innings, and 55,996 batters faced from Basic2
- 08KBO Record Room — Team records (batting)2026 regular season plate appearances, 56,732 (used as league batters faced)
- 09KBO Record Room — Player records (pitching)Innings, walks and strikeouts of the 18 qualified pitchers in the 2026 regular season
- 10MLB Stats API — 2026 team pitching30 teams: 40,700 strikeouts, 16,337 walks, 43,079⅔ innings, 183,849 batters faced; the 46 qualified pitchers come from the qualified list of the same API
- 11NPB — 2026年度 セントラル・リーグ チーム投手成績Together with the Pacific League page (tmp_p.html), 12 teams: 13,430 strikeouts, 4,841 walks, 15,276 innings, 63,898 batters faced; 2025 on the 2025 page of the same address: 12,475, 4,559, 64,178
- 12NPB — 2026年度 セントラル・リーグ 個人投手成績（規定投球回以上）Together with the Pacific League page (pit_p.html), 22 pitchers
- 13Baseball-Reference — 2025 Major League Baseball Standard Pitching2025 league totals: 40,645 strikeouts, 15,379 walks, 43,075 innings, 182,926 batters faced
Frequently asked questions
How do you calculate K/BB?
Divide strikeouts by walks. MLB's official glossary defines K/BB as the number of strikeouts a pitcher records for each walk he issues, found by dividing total strikeouts by total walks. With 180 strikeouts and 48 walks, 180 ÷ 48 = 3.75. Innings pitched and batters faced are not part of the formula.
What is a good K/BB?
There is no official scale. Neither the MLB glossary nor the FanGraphs Library sets K/BB tiers, so the sound approach is to compare with the same season's league average. In the 2026 regular season the averages were 2.49 in MLB, 2.77 in NPB and 2.08 in KBO, and the median among qualified pitchers was 3.19 in MLB, 4.15 in NPB and 3.24 in KBO. For a starter, the qualified median is the fairer yardstick than the league average.
What happens to K/BB when a pitcher has no walks?
It cannot be divided by zero, so the value is undefined. This calculator shows ∞ when there are strikeouts and only says the line is higher than every qualified pitcher. K/BB also swings a lot when walks are few. With 24 strikeouts and 2 walks, one walk more or fewer moves it from 8.00 to 24.00, so enter batters faced as well and read K% − BB% alongside it.
What is the difference between K/BB and K% − BB%?
K/BB divides strikeouts by walks. K% − BB% subtracts the share of batters walked from the share struck out. In a 2010 post, Tom Tango found that two groups of pitchers with the same K/BB of 2.0 allowed 4.26 and 4.94 runs per nine, a gap of almost 0.7, while groups with a similar margin allowed similar runs. He concluded that the difference matters more than the ratio. Pick "Same difference line" on the slope chart to see real 2026 pitchers with similar K/BB but a different margin.
How are K/BB and K/9 and BB/9 related?
K/BB = K/9 ÷ BB/9, because both are divided by the same innings. With a K/9 of 9.80 and a BB/9 of 2.61, 9.80 ÷ 2.61 ≈ 3.75, the same as K/BB. That is why, when walks per nine are plotted across and strikeouts per nine up, pitchers with the same K/BB sit on one straight line out from the origin. The slope chart above is that picture.
Do hit batters and intentional walks count as walks?
A hit by pitch does not. The MLB glossary records it separately from a walk, so adding it would push K/BB below its true value. An intentional walk is scored as a walk and is included in the official MLB and NPB walk totals, so it goes into your walk count.
Why compare with qualified pitchers?
Rate stats swing wildly for pitchers with few innings, so official rankings include only those with at least 1.0 inning per team game (MLB Rule 9.22, in the glossary's Rate Stats Qualifiers). In 2026 the qualifier was 144 innings in KBO, 162 in MLB and 143 in NPB, and 18, 46 and 22 pitchers met it. The league average also includes every pitcher who fell short of the qualifying mark, so a starter who works deep into games is better compared with the qualified group.
Why is the 2026 MLB average lower than 2025?
Walks rose and strikeouts barely moved. MLB walks went from 15,379 in 2025 to 16,337 in 2026, while strikeouts were almost the same at 40,645 and 40,700. The league K/BB therefore fell from 2.64 to 2.49. Holding a 2026 line against the 2025 average would make it look worse than it is, so use the same season's average.