What Is 3-Up, 3-Down in Baseball? The 1-2-3 Inning Explained
3-up, 3-down in baseball means a pitcher faced exactly three batters in an inning and retired all three, allowing no baserunners. It is the same thing as a 1-2-3 inning — the cleanest possible half-inning of work and the building block of a perfect game.
What Is 3-Up, 3-Down in Baseball?
3-up, 3-down describes the cleanest half-inning a pitcher can throw: three batters come to the plate, and all three are retired, with nobody reaching base. No hits, no walks, no hit batters, no errors that let a runner on — just three outs on the minimum number of hitters. It is the same thing announcers mean when they say a pitcher worked a 1-2-3 inning: he faced the three hitters due up (the one, two, and three spots in the sequence of batters that inning) and set them all down in order. It is the basic unit of a dominant outing and the building block of the rarest pitching feats.
What Does 3-Up, 3-Down Mean Exactly?
Literally: three batters came up to bat, and all three went down (were retired). The phrase counts batters, not outs in isolation — the key is that exactly three hitters came to the plate, which is only possible if none of them reached base. A pitcher can record three outs in an inning while still giving up a hit and a walk (he'd face more than three batters), and that is *not* 3-up, 3-down. The out types do not matter: three strikeouts, three groundouts, a strikeout and two flyouts — any combination of three outs against the three batters due up qualifies. What it rules out is any baserunner at all.
How Is 3-Up, 3-Down Different From a Perfect Game?
A 3-up, 3-down inning is one clean half-inning; a perfect game is *every* half-inning being 3-up, 3-down for a full game. To throw a perfect game, a pitcher (or a pitching staff, though it's almost always one starter) must retire all 27 batters in order — 27 up, 27 down — with no hit, walk, hit batter, or error allowing a single baserunner across nine innings. So a perfect game is nine consecutive 1-2-3 innings, the rarest of all pitching achievements. A no-hitter is a step below: no hits allowed, but walks or errors may have put runners on, so a no-hitter does not require every inning to be 3-up, 3-down.
Is 3-Up, 3-Down the Same as an Immaculate Inning?
No — they are easy to confuse but distinct. A 3-up, 3-down inning only requires that the three batters be retired by any means. An immaculate inning is a much rarer special case: three strikeouts on exactly nine pitches, striking out the side on the minimum number of pitches possible. Every immaculate inning is also 3-up, 3-down, but the vast majority of 1-2-3 innings are not immaculate — a pitcher who gets three groundouts on six pitches threw a clean 3-up, 3-down inning that was nowhere near immaculate. Think of immaculate as the maximally efficient, maximally dominant subset of a clean inning.
Worked Example
Top of the fifth, the starter takes the mound protecting a one-run lead. He gets a groundout to short, a swinging strikeout, and a lazy flyout to center — three batters up, three batters down, no one reaching base. That is a 3-up, 3-down inning, also called a 1-2-3. If he had walked the leadoff hitter before retiring the next three, he'd have recorded three outs but faced four batters — not 3-up, 3-down. String nine of these clean innings together with no baserunners at all and the same pitcher has thrown a perfect game; make all three of these outs strikeouts on nine total pitches and that single frame becomes an immaculate inning.
Why 3-Up, 3-Down Matters
3-up, 3-down is the simplest measure of a dominant inning: the pitcher controlled the frame completely and handed his offense a fresh slate with no traffic on the bases. Stringing clean innings together keeps pitch counts down, limits scoring chances to zero, and is the path to the perfect game and other milestone outings. It's also a tempo and momentum marker — a starter who keeps going 1-2-3 stays in the game longer and keeps his defense engaged, while an inning with baserunners raises pitch count and pressure. When you hear "he's been 3-up, 3-down all night," it means the opposing lineup hasn't put a single man on.
In Legends Deck
Legends Deck resolves each half-inning batter by batter, weighing a pitcher card's stuff and command against the hitters due up — so a clean 3-up, 3-down frame is the engine retiring all three batters with no baserunner reaching, exactly as in a real 1-2-3 inning. Stack enough of them and a card can chase a perfect game or, on nine pitches and three whiffs, an immaculate inning. See how the engine turns real Statcast stuff into pitching ratings in how card ratings work, or browse the inputs on the leaderboards hub.