What is BB/9 in Baseball?
Walks Per Nine Innings · Pitching
BB/9, or walks per nine innings (also written BB/9 or BB9), measures how many free passes a pitcher issues per nine-inning span. It is the standard rate stat for evaluating a pitcher's command of the strike zone. A low BB/9 indicates consistent strike-throwing and the ability to put hitters in unfavorable counts. Walks extend innings, increase pitch counts, and put runners on base without a batter earning it — making BB/9 a critical component of any pitching assessment.
Formula
BB/9 = (Walks × 9) ÷ Innings Pitched
A pitcher who walks 27 batters in 162 innings has a BB/9 of 1.50. One who walks 54 batters in 162 innings has a BB/9 of 3.00, indicating significantly worse command despite identical workload.
Benchmarks
| Level | BB/9 |
|---|---|
| Elite | < 1.5 |
| Excellent | 1.5–2.0 |
| Above Average | 2.0–2.5 |
| Average | 2.5–3.5 |
| Below Average | > 4.0 |
ALL-TIME CAREER BB/9 LEADERS
| Rank | Player | BB/9 |
|---|---|---|
| 1 | Candy Cummings | 0.47 |
| 2 | Tommy Bond | 0.48 |
| 3 | Al Spalding | 0.51 |
| 4 | Cherokee Fisher | 0.54 |
| 5 | Jim Devlin | 0.58 |
| 6 | George Bradley | 0.60 |
| 7 | George Zettlein | 0.60 |
| 8 | Terry Larkin | 0.71 |
| 9 | Sam Weaver | 0.73 |
| 10 | Dick McBride | 0.75 |
BEST SINGLE-SEASON BB/9 IN MLB HISTORY
| Rank | Player | Year | Team | BB/9 |
|---|---|---|---|---|
| 1 | Candy Cummings | 1875 | HR1 | 0.09 |
| 2 | Joe Blong | 1875 | SL1 | 0.14 |
| 3 | Tommy Bond | 1874 | BR2 | 0.14 |
| 4 | Tommy Bond | 1875 | HR1 | 0.18 |
| 5 | George Zettlein | 1875 | CH2 | 0.19 |
| 6 | Cherokee Fisher | 1875 | PH2 | 0.23 |
| 7 | George Zettlein | 1876 | PHN | 0.23 |
| 8 | Cherokee Fisher | 1876 | CN1 | 0.24 |
| 9 | Bill Stearns | 1875 | WS6 | 0.26 |
| 10 | George Bradley | 1880 | PRO | 0.28 |
HISTORICAL CONTEXT
Command has always been central to pitching success. Cy Young, whose name graces the annual award for the best pitcher in each league, walked only 1.5 batters per nine innings over his legendary career — elite by any era's standards. Christy Mathewson and Grover Cleveland Alexander were similarly renowned for their pinpoint control in the Dead Ball Era.
Greg Maddux is the modern gold standard for command. His career BB/9 of approximately 1.8 over 23 seasons ranks among the lowest ever for a power-era starter. Maddux famously painted the corners of the strike zone and rarely issued unintentional walks, relying on precision rather than velocity to retire hitters. He won four consecutive Cy Young Awards (1992–1995) while averaging over 34 starts per season.
The tradeoff between strikeouts and walks is captured in the K/BB ratio — strikeouts divided by walks — which many analysts use as a single control metric. Pitchers like Pedro Martínez and Randy Johnson combined elite K/9 with solid BB/9, making them particularly dangerous. Pitchers who miss bats at the cost of walks often see their ERAs fluctuate more than their FIPs suggest.
Modern pitching development emphasizes command alongside velocity and spin rate. Teams track pitch tunneling and zone percentage (fraction of pitches thrown in the strike zone) as leading indicators of future BB/9 performance. A pitcher who demonstrates improving command in the minors is often considered a safer bet than one whose only calling card is raw stuff.
FREQUENTLY ASKED QUESTIONS
What is BB/9 in baseball?
BB/9, or walks per nine innings (also written BB/9 or BB9), measures how many free passes a pitcher issues per nine-inning span. It is the standard rate stat for evaluating a pitcher's command of the strike zone. A low BB/9 indicates consistent strike-throwing and the ability to put hitters in unfavorable counts. Walks extend innings, increase pitch counts, and put runners on base without a batter earning it — making BB/9 a critical component of any pitching assessment.
How is BB/9 calculated?
BB/9 is calculated by multiplying total walks allowed by 9 and dividing by total innings pitched. This normalizes walks to a per-nine-inning rate, allowing fair comparison between pitchers who throw different numbers of innings.
What is a good BB/9 in baseball?
In the modern era, a BB/9 below 2.0 is elite; 2.0–2.5 is excellent; 2.5–3.5 is average; above 4.0 is below average. Low BB/9 is one of the most stable year-to-year pitching skills — pitchers who command the zone consistently tend to maintain that trait across seasons.
What is the difference between BB/9 and BB%?
BB/9 (walks per nine innings) is an innings-based rate, while BB% (walk rate) is calculated as walks divided by total batters faced. BB% is generally preferred in modern analysis because it measures what fraction of hitters a pitcher walks, without distortion from varying game pace or different handedness matchups. Both metrics tell the same story directionally — lower is better — but BB% is slightly more precise.
Does BB/9 include intentional walks?
In most standard contexts, BB/9 includes all walks — both intentional (IBB) and unintentional. Many analysts prefer to exclude intentional walks because they are a strategic managerial decision rather than a reflection of pitching command. When intentional walks are excluded, the stat is sometimes listed as uBB/9 or unintentional BB/9. The Lahman database tracks IBB separately, but most published BB/9 figures include all walks.
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