How MLB Works
Major League Baseball is a 30-team league split into two leagues of 15. The regular season runs from late March through late September, and each team plays 162 games. The postseason runs through October and features four rounds, culminating in the World Series.
Season at a glance
- Late Mar—late Sep: Regular season. 162 games per team across roughly 26 weeks.
- Early Oct: Wild Card Series. Best of 3, all at the higher seed’s park.
- Mid Oct: Division Series (ALDS / NLDS). Best of 5.
- Mid—late Oct: League Championship Series (ALCS / NLCS). Best of 7.
- Late Oct—early Nov: World Series. Best of 7.
Leagues, Divisions, and the Regular Season
The 30 teams are split into the American League (AL) and the National League (NL). Each league has three five-team divisions: East, Central, and West. Divisions matter more than they do in the NBA—winning your division automatically clinches a top-3 playoff seed and a first-round bye.
Each team plays 162 games: 52 against its own division (13 vs each of 4 rivals), 64 against the other two divisions in its league, and 46 against the other league (interleague). After 162 games, teams are sorted by win percentage. The top three division winners in each league get the top three seeds; the next three best non-division-winners get the wild card spots (seeds 4–6).
Six teams from each league make the postseason—twelve total. Fourteen teams don’t. MLB’s long regular season is famously punishing; a team can play well for 145 games and still miss October because of a hot finish from a rival.
Tiebreakers (No More Game 163)
Through 2021, MLB broke ties for playoff seeding with an actual 163rd game. That ended in 2022: now ties are broken by formula, not by playing an extra game.
1. Head-to-head record: Who won the season series between the tied teams?
2. Intradivision record: If still tied, better record against teams in their own division wins.
3. Intraleague record: If still tied, better record against teams in their own league.
4. Last-half intraleague record: Most recent ~81 games against same-league opponents.
For three-way ties, the same tiebreakers apply in order until a team is separated, then the remaining two go through the list again. The change matters most in late September: a team can clinch a division on the second-to-last day even while losing, if it owns the head-to-head tiebreaker.
The Postseason
Twelve teams make the playoffs—six per league. Each league’s bracket is independent until the World Series. The top two division winners (seeds 1 and 2) get a first-round bye; the other four teams (seed 3 + three wild cards) play the Wild Card Series. Brackets are fixed—there’s no re-seeding between rounds.
Round 1 — Wild Card Series: 3 vs 6 and 4 vs 5 in each league. Best of 3, all at the higher seed’s park.
Round 2 — Division Series (ALDS / NLDS): Wild Card winners face the seeds 1 and 2 (who got byes). Best of 5.
Round 3 — League Championship Series (ALCS / NLCS): Each league’s two DS winners face off. Best of 7. Winner is league pennant champion.
Round 4 — World Series: AL champion vs NL champion. Best of 7.
Wild Card Series (Best of 3)
The Wild Card Series is a quick gauntlet. The higher seed hosts all three games (Games 1, 2, and 3 if necessary)—there’s no traveling for the lower seed. Win two games and you’re on to the Division Series; lose two and your season is over.
The all-home format is a big advantage for the higher seed (you don’t face a road game), but the short series adds significant variance—a hot starting pitcher can carry an underdog through. The format was added in 2022 to make division-winning matter more (top-2 seeds get a bye + no Wild Card stress).
Division Series (Best of 5)
The two seeds 1–2 in each league host the Wild Card winners in a best-of-5 series, first team to three wins advances. Format is 2-2-1: higher seed hosts Games 1, 2, and 5; lower seed hosts Games 3 and 4.
Best-of-5 is short enough that a team riding momentum from the Wild Card can absolutely beat a 100-win division winner. It’s the round where the rested-bye advantage and the fresh-from-winning-WCS advantage collide.
League Championship Series (Best of 7)
Each league’s two Division Series winners meet in the ALCS (American League Championship Series) or NLCS (National League Championship Series). Best of 7, first to four wins. Format is 2-3-2: higher seed hosts Games 1, 2, 6, and 7; lower seed hosts Games 3, 4, and 5.
The winners are the AL Pennant Champion and NL Pennant Champion. The trophy isn’t the World Series trophy—but winning your league’s pennant is a major accomplishment in its own right.
The World Series
The World Series is the championship round—American League champion vs National League champion, best of 7. Format is 2-3-2: the home-field team hosts Games 1, 2, 6, and 7. Home-field advantage in the World Series goes to whichever league champion had the better regular-season record (rule changed from the All-Star Game outcome in 2017).
Games typically start in late October and wrap by early November. The World Series winner is MLB’s undisputed champion.