Betting on the Postseason: Series Prices and Game Prices
How a playoff series price is built from single-game odds, with worked examples of best-of-three, five and seven math, how vig and futures change the picture, and why series prices move after every game.
A playoff series price and a single-game price are two views of the same event, and the arithmetic that connects them is simpler than most bettors expect. If a team is a modest favorite in each game, its chance of winning a seven-game series is noticeably larger than its chance in any one game, because the weaker team has to win four times before the stronger team wins four. A team that is a 60 percent favorite in every game is about a 71 percent favorite to win a best-of-seven series. That is the whole idea, and the rest of this article is the working out.
This is an educational explanation of how prices relate to each other. It is not a recommendation to bet, it contains no picks and no tips about any team or game, and nothing here guarantees a profit. Sports betting carries a real risk of loss, it is for adults of legal age and only where it is legal, and the odds used below are invented for illustration, not quotes from any sportsbook. If gambling is causing you problems, the national helpline is 1-800-GAMBLER, and the National Council on Problem Gambling publishes help at ncpgambling.org.
Understanding series pricing is useful even for a reader who never places a wager. It explains why a favorite listed at a shorter price for the series than for each game is not being overrated, and why the price swings so much after a single result.
The format that the prices sit on
Postseason prices only make sense against the structure of the playoffs. As of the 2025 season, 12 teams make the field, six from each league: three division winners and three wild-card teams. The two division winners with the best records skip the first round. The other four teams in each league meet in a best-of-three wild-card series, in which the higher seed hosts all three games. The division series is best-of-five, and the league championship series and the World Series are best-of-seven. The official rules and any change to them are published by MLB, and readers should check them before relying on any detail here.
The format has changed several times. From 2012 to 2021 the wild-card round was a single game. In 2020 a larger field played a best-of-three first round. The World Series itself was best-of-nine in 1919, 1920 and 1921, which is why the 1919 Series that the White Sox lost to Cincinnati ended three games to five. It has been best-of-seven since 1922, and the history is in the history of the World Series.
Home games are split unevenly. In a best-of-five the higher seed hosts games 1, 2 and 5, in a 2-2-1 pattern. In a best-of-seven it hosts games 1, 2, 6 and 7, in a 2-3-2 pattern. The pattern matters to a series price because the team with the extra home game gets a small edge in the deciding game, but the edge is small, and it is one reason the price for a series is not just a mechanical function of an average game.
From a game price to a series price
Start with the simplest model. Suppose Team A has the same probability, p, of winning each game, and games are independent of one another. A best-of-seven series ends when one team reaches four wins. Team A wins the series if it wins four games before Team B does, and the probabilities add up over the possible lengths of the series: winning in four, in five, in six or in seven.
You do not need to do that sum by hand. The results for a range of game probabilities are below.
| Team A chance per game | Best-of-three | Best-of-five | Best-of-seven |
|---|---|---|---|
| 50% | 50.0% | 50.0% | 50.0% |
| 52% | 53.0% | 53.7% | 54.4% |
| 55% | 57.5% | 59.3% | 60.8% |
| 58% | 61.9% | 64.7% | 67.1% |
| 60% | 64.8% | 68.3% | 71.0% |
| 65% | 71.8% | 76.5% | 80.0% |
Two patterns stand out. The longer the series, the more it favors the better team, because there is more time for the stronger side to win out over luck. And a small edge per game grows slowly: a team that is 55 percent per game, a figure that would look like a modest favorite on a game board, is a 60.8 percent favorite in seven games. Even a 65 percent per-game favorite, which in baseball is a heavy favorite, wins a best-of-seven only four times in five.
That second pattern is why baseball is considered among the hardest of the major sports to predict in a short series, and it is the subject of why baseball favorites lose so often. Single-game prices between two playoff teams usually imply a favorite somewhere between 50 and 65 percent, and at 60 percent per game the favorite still loses a seven-game series 29 percent of the time.
A worked example, with the vig removed
Suppose a sportsbook lists a game at -150 for the favorite and +130 for the underdog. Those prices are illustrative. Converting each to an implied probability, the method explained in converting baseball betting odds to implied probability, gives 150 divided by 250, or 60.0 percent, for the favorite, and 100 divided by 230, or 43.5 percent, for the underdog.
Those two numbers add up to 103.5 percent. The excess over 100 is the sportsbook's margin, the vig, which is explained in what the vig is and how sportsbooks make money on baseball. To estimate the market's own view of the game, divide each by the total. The favorite becomes 57.98 percent and the underdog 42.02 percent.
Now carry the fair figure into the series. A team with a 57.98 percent chance per game wins a best-of-three about 61.9 percent of the time, a best-of-five about 64.7 percent and a best-of-seven about 67.0 percent. A fair price for the favorite in a seven-game series would be roughly -203, because a 67.0 percent chance corresponds to odds of about 2.03 to 1. A sportsbook will add its own margin, so the price actually offered would usually be a little worse than that for both sides.
The conversion also works backward. If a seven-game series is listed at -245 for the favorite, its implied probability is 245 divided by 345, or 71.0 percent. Under the same simple model, that corresponds to a per-game chance of about 60 percent. A bettor can use that to ask whether a series price is consistent with the game prices on the board.
How series prices move after every game
A series price is not fixed. After each game, the state of the series changes and the price moves with it. The table below keeps the same illustrative 60 percent per game favorite in a best-of-seven and shows the chance of winning the series from each score, still under the simple model.
| Series score (favorite first) | Favorite wins series |
|---|---|
| 0-0 | 71.0% |
| 1-0 | 82.1% |
| 0-1 | 54.4% |
| 2-0 | 91.3% |
| 0-2 | 33.7% |
| 1-1 | 68.3% |
| 2-1 | 82.1% |
| 1-2 | 47.5% |
| 3-1 | 93.6% |
| 1-3 | 21.6% |
| 2-2 | 64.8% |
| 3-2 | 84.0% |
| 2-3 | 36.0% |
| 3-3 | 60.0% |
The jumps are large. Losing game one costs the favorite 16.6 percentage points, from 71.0 to 54.4 percent, which is why a series price can swing from a clear favorite to nearly even money after one game. Down 0-2, the favorite falls to 33.7 percent. A favorite that trails 1-3 still has about a one in five chance under the model, which is consistent with comebacks from that position happening occasionally.
The 1-3 row is easy to check by hand. A favorite that trails 1-3 must win three games in a row, and 0.6 times 0.6 times 0.6 is 0.216, or 21.6 percent. In the simple model, past results change the state of the series but do not change the strength of either team.
Series length and the games-played market
Sportsbooks also offer markets on how many games a series will last, or on an exact result such as the favorite winning in six. These prices come from the same model. For a best-of-seven, the chance of each length is below.
| Series length | Evenly matched teams | 60 percent favorite per game (either team wins) |
|---|---|---|
| 4 games | 12.5% | 15.5% |
| 5 games | 25.0% | 26.9% |
| 6 games | 31.25% | 30.0% |
| 7 games | 31.25% | 27.6% |
Two teams of equal strength play a seven-game series nearly a third of the time. When one team is a clear favorite, shorter series become likelier and a full seven games less so, though the changes are modest. A bettor who sees an over-under of 5.5 games on a series is looking at a market in which, for two equal teams, the four-game and five-game results add up to 37.5 percent and the six-or-seven total is 62.5 percent. The over is therefore the likelier side before any margin, and a stronger favorite shifts a little weight toward the under.
Where the simple model fails
The model assumes the same win probability in every game, and real series break that assumption in four ways.
- Starting pitchers. The probability of winning a given game depends heavily on who starts it. A team with one dominant starter is a stronger favorite in the games he starts and a weaker one in the others. Series prices are built from the expected rotation, and a change in the plan, an injury or a rainout can move the price.
- Bullpen use. Relievers who pitch in one game may be unavailable the next, so the state of the bullpen carries from game to game.
- Home field. Home teams win somewhat more than half their games, so the 2-3-2 and 2-2-1 patterns tilt the per-game odds from game to game.
- Rest and injuries. An off-day in the schedule helps a team lean on its best pitchers, and an injury to a key hitter changes everything after it occurs.
Because of these effects, a bettor cannot simply multiply game prices together. The market uses richer models, and the clean tables in this article are a guide to the order of magnitude, not a replacement for them. The independence assumption is also strained in a different way: a surprising result may reveal that a team is better or worse than the market thought, so prior results are not entirely irrelevant.
Futures: compounding across rounds
The price to win the World Series, a futures price, is a series price multiplied across several rounds. A team that is a 65 percent favorite to win a division series, 60 percent to win a league championship series and 55 percent in the World Series has a title chance of 0.65 times 0.60 times 0.55, which is about 21.5 percent. That figure is much lower than any of the individual series chances, and it is the reason the favorite in a World Series futures market is typically priced at a long number even if it is the best team.
Futures markets carry a larger margin than single games. If you convert every team's futures price to an implied probability and add them up, the total is often well over 100 percent, sometimes by a wide amount. That excess is the book's hold, and it is larger than the margin on a game because there are more outcomes and more uncertainty. A bettor comparing a futures price with a fair figure should first remove the margin, using the same normalizing step shown above, but across all teams.
The same arithmetic explains why regular-season markets work the way they do. Win totals, covered in season win totals: how they are set and what they mean, are another way of expressing a team's strength, and the playoff chances flow from that strength.
Comparing prices and keeping the risk in view
Prices for the same game and series differ between sportsbooks, and the differences matter more at the long end. The step-by-step method for comparing them is in how to compare odds and shop for lines. The site's odds page displays current lines, and the stat calculator can help with the arithmetic.
It is worth being plain about the risk. A book's margin means that an average bettor loses money over time, and a short series is a small sample in which an excellent team can easily lose. A model that says a team has a 71 percent chance also says it has a 29 percent chance to lose. Any bet should be sized so that losing it does not matter, and a person who finds that betting is affecting work, relationships or finances should stop and call 1-800-GAMBLER.
Common questions
Is a team's series price always shorter than its game price? For the favorite, yes: the same per-game edge is worth more over several games. The underdog's price gets longer in the series for the same reason.
Why do prices change so much after game one? The state of the series changes, and the model shows the favorite's chance dropping from 71.0 to 54.4 percent after one loss in the example. Information about starting pitchers and injuries also arrives.
Can I add the game prices to get a series price? No. Series chances come from combining many possible sequences of wins and losses, not from adding or multiplying the prices for single games.
Does a bigger series favor the underdog or the favorite? The favorite. A longer series gives the better team more chances to win out, as the table of best-of-three, five and seven shows.
Do fantasy leagues work the same way? No. A fantasy league scores individual players, and the commissioner's job is described in how to run a fantasy baseball league as commissioner. The playoff structure there is set by the league, not by a market.
Where to go next
For the tiebreakers that decide who reaches the postseason in the first place, read how MLB tiebreakers work. The baseball betting topic page collects current coverage. If you or someone you know has a problem with gambling, call 1-800-GAMBLER or visit the National Council on Problem Gambling.