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An immaculate inning is when one pitcher strikes out all three batters in a half inning using exactly nine pitches, meaning every single pitch is a strike. No balls, no fouls after two strikes, no balls put in play. It is the cleanest possible half inning a pitcher can throw.
The exact requirements
The arithmetic leaves no room. Three batters, three strikes each, nine pitches total. Every pitch must be either a called strike, a swinging strike, or a foul ball on the first or second strike. A single ball outside the zone ends the attempt, and so does a foul ball with two strikes, because that adds a tenth pitch.
- One pitcher must throw all nine pitches.
- All three batters must strike out.
- The count must never reach a single ball.
- No batter may put a ball in play, even for an out.
Why it stays rare
Strikeouts are more common in the modern game than they have ever been, which has made the feat less exotic than it once was. It is still uncommon, because it requires the hitters to cooperate in a specific way. A hitter who takes a borderline pitch for a ball ends it. A hitter who fouls off a two strike pitch, the most ordinary event in baseball, ends it too.
Major League Baseball and sites like Baseball Reference track the running total, so if you want the current count, look it up there rather than trusting a number in an old article. The figure moves every season.
How it compares to other pitching feats
| Feat | What it requires | Scope |
|---|---|---|
| Immaculate inning | Three strikeouts on nine pitches, all strikes | One half inning |
| Perfect inning | Three batters, three outs, any way | One half inning |
| No hitter | No hits allowed, walks and errors permitted | Full game |
| Perfect game | No batter reaches base at all | Full game |
Notice that an immaculate inning and a perfect game measure different things. One is about maximum efficiency in a tiny window, the other about sustained flawlessness across nine innings.
The oddities fans argue about
Two quirks come up constantly. The first is the four strikeout inning, which sounds impossible until you remember the dropped third strike rule. If the catcher fails to cleanly hold strike three, the batter can run to first, and the inning continues with an extra strikeout on the books. That inning cannot be immaculate, because it required more than nine pitches.
The second is that an immaculate inning does not guarantee a scoreless one for the pitcher’s team, or even a win. It is a nine pitch half inning, nothing more. Pitchers have thrown one and lost the game, which is a useful reminder that baseball records reward precision in moments rather than outcomes.
