BB/9 Calculator
Calculate walks per nine innings (BB/9) from walks allowed and innings pitched.
Informational only — not a substitute for official league statistics or professional judgment.
How it's calculated
Assumptions
- Uses nine innings by definition — BB/9 is always expressed per nine innings regardless of a league's game length.
- Counts walks only (including intentional walks); hit-by-pitches are excluded per the official definition.
- Innings pitched must be entered in standard baseball notation (.0, .1, or .2 for 0, 1, or 2 outs) — not tenths of an inning.
Source: MLB Glossary — Walks per Nine Innings (BB/9)
Last reviewed: July 2026
Frequently asked questions
What's considered a good BB/9?
Lower is better. In recent MLB seasons league average has sat around 3.0–3.3 walks per nine innings; under 2.0 reflects excellent command, and 4.0 or higher usually signals real control problems.
Do hit-by-pitches or intentional walks count in BB/9?
Intentional walks count — they're recorded as walks in the official statistics. Hit-by-pitches do not count as walks, even though they also put the batter on first base; they're a separate stat (HBP).
Why does innings pitched use .1 and .2 instead of normal decimals?
Baseball box scores record partial innings in thirds, not tenths: .1 means one out recorded (1/3 of an inning) and .2 means two outs recorded (2/3 of an inning). This calculator converts that notation to real innings automatically before computing BB/9.
How is BB/9 different from BB% (walk percentage)?
BB/9 counts walks per nine innings, while BB% counts walks per batter faced. Analysts often prefer BB% because pitchers who allow many baserunners face more batters per inning, which can distort per-inning rate stats like BB/9.
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