How to bet on MLB on Polymarket: moneylines, run lines, totals, NRFI, and player props

Polymarket listed 121,605 markets on 2,229 MLB games from March 25 to September 12, 2026, about 55 a game. Most of them barely traded: in September 2026 an MLB game had 10.7 that traded 1,000 shares or more.

The core of every game is one moneyline, 7.1 total lines and 5.9 run lines on average. From June 10, 2026, about half the season's games also listed first-five-innings totals, winners and spreads, an extra-innings market, pitcher strikeout props and home run props, 31.4 home run markets a game.

Polymarket titles each game with the away team first, "Texas Rangers vs. Arizona Diamondbacks" for the Rangers at the Diamondbacks, and the moneyline pays $1 a share on the team that wins. The menu on a game page is mostly listings; the next section shows where the money went.

Across 2,229 MLB games from March 25 to September 12, 2026, Polymarket reported $1.79 billion in volume, counting each share traded at its $1 face value, so the cash that changed hands was less. The moneyline took 71.3% of it, totals 20.8% and the run line 7.0%. The first-inning markets took 0.6%, $10.6 million, and every other family together took less than half a percent.

That volume split is a map of liquidity. The 37,438 home run markets of the season drew $1.3 million of that volume between them, so a large order on a prop moves its price in a way the same order on a moneyline does not. Check a market's volume on its page before you size a bet.

Orioles at Yankees on September 27, 2026 was rained out and never made up, and every one of its markets paid 50 cents a share; the largest, the O/U 7.5, had 66,298 shares of volume. A game that is postponed and made up is different: its markets stay open and settle on the makeup game.

The other 10 splits could each happen to you. Pittsburgh named Jared Jones to start on September 2, 2026, Bubba Chandler started instead, and the Jones strikeout lines paid 50-50. Spring training games can end tied, and a playoff game a series never needs splits its moneyline.

A run line such as "Spread: Chicago Cubs (-1.5)" resolves to the Cubs if they win by 2 or more runs and to their opponent otherwise. A total such as "O/U 10.5" resolves Over at 11 or more combined runs. The first-inning market resolves Yes if either team scores in the 1st, and first-five-innings markets settle on the score after the 5th, a tie resolving the winner market to Draw and the spread to the team getting the runs.

Player props differ by role. A hitter prop counts the whole game, extra innings included, and resolves Under if the hitter does not take the field. A pitcher prop resolves 50-50 if the named pitcher does not start, and on his final line if he starts and leaves early. Check the lineup before you buy a hitter's Over.

A Polymarket share pays $1, so its price is a probability. A team at 58¢ is a 58% chance to win, and the other team trades near 42¢. Buy $100 of the 58¢ side and you hold about 172 shares that pay about $172 if the team wins.

Sportsbook odds convert the same way, and the chart above draws that conversion across the range. A favorite at -138 is 138 divided by 238, 58%; an underdog at +138 is 100 divided by 238, 42%.

A sportsbook's two sides add up to more than 100%, while the two sides of a Polymarket market add up to about $1. The cost of trading is the spread and, on a taker order, Polymarket's fee.

MLB home teams won 53.7% of 4,521 regular-season and postseason games settled on Polymarket, nearly all from the 2025 and 2026 seasons, with a half-width of 1.45 points: 54.1% in 2025 and 53.2% in 2026.

MLB's 53.7% ties the NFL for the smallest home edge of the 5 US pro leagues in the home field study, and with 8 times the NFL's sample it is the better-measured of the two.

The price already carries it. Large Polymarket bets on MLB home sides and away sides each came in within about a third of a point of what they paid, so a home team is not a bet in itself.

One-run games decide the run line, and 29.1% of 1,882 MLB games settled on Polymarket were decided by exactly one run, with a half-width of 2.05 points. The chart above shows the rate month by month.

In a one-run game every +1.5 bet wins and every -1.5 bet loses, whichever team won. The run line is baseball's spread, and its standard number is 1.5 runs: a favorite at -1.5 has to win by two, and an underdog at +1.5 wins the bet by winning the game or losing by one.

Polymarket lists more than one line for most games, for both teams. The Rangers and Diamondbacks game on September 13 listed the Rangers from -1.5 to -5.5 and the Diamondbacks at -1.5 and -2.5. The point spread guide covers spreads across sports.

Under hit 49.7% of 14,633 MLB total lines on 2,149 games settled from April 2 to September 13, 2026, an interval from 48.2% to 51.2% that includes a coin flip. An MLB total is a ladder of lines, each paying Over or Under on the combined runs, and the over/under guide covers how totals are priced across sports.

Large buyers found no lean either. Over buyers came in +1.13 points against the price they paid, an interval from -2.52 to +4.77, and Under buyers -2.25, from -6.13 to +1.81; both include zero. If you buy an MLB total, buy it because you have a read on the game that the line lacks, not because one side tends to win.

No run scored in the first inning of 49.4% of 2,237 MLB games with a settled market from September 2025 to September 12, 2026. NRFI means no run first inning: the No side of Polymarket's first-inning market, and Yes is YRFI.

The home team scored in the bottom of the first in 32.7% of games and the away team in the top in 26.4%, as the chart above shows.

At first pitch the no-run side cost 51.4¢ on average, about 2 points more than it hit. $1 on NRFI in every game lost 6.38% after Polymarket's sports taker fee, an interval that excludes zero, while $1 on YRFI returned plus 2.28%, inside the noise. Team NRFI records spread no wider than chance would produce. The full numbers are in the NRFI study.

Before April 2, 2026 the market was titled "NRFI: <away> vs. <home>" and Yes paid when no run scored. Read a market's rules before you read its price.

A first-five-innings winner market is three-way, and the Draw comes in more often than its name suggests: 375 of 2,429 completed 2026 regular-season games, 15.4%, were level after five, give or take 1.44 points. Check the Draw's price against that rate before you buy either team.

The extra-innings market pays Yes once the 10th inning starts, and 209 games got there. Inning winner markets pay on which team scores more runs in one inning, with a Draw when neither does.

These markets are listed far more than they are traded: the first-five winner family drew 0.04% of MLB's reported volume from March 25 to September 12, 2026. On a book that thin, your order can set the price, so place it as a limit order.

Baseball money arrives with the lineups, which clubs post a few hours before first pitch. Of 1,234 MLB buys of $10,000 or more from September 10 to October 10, 2026, 33.5% landed after first pitch, against 39.6% in the NFL, so by first pitch a baseball price has already met 66.5% of the large money.

In play, the price moves with every run. To take a position off during the game you sell your shares, and the cash-out guide covers when that makes sense. Either way, a limit order at your price keeps you from chasing a moving line, and a resting order that fills pays no fee: Polymarket charges only the taker.

D and F are the bottom grades 0xinsider gives a wallet on its settled results, and on MLB games those wallets did most of the large buying. From September 20 to October 10, 2026, 49 of them placed more large buys than every S, A and B wallet together.

The MLB board lists live and upcoming games with an active Polymarket market. Each card shows both teams' prices and chances, the 24-hour move, and the inning and score for a live game. Under Details, free on every card, sit the most traded props and the top 5 holders on each side with their grades and baseball win rates. On the event page, volume by market family and the full Top holders list are Pro.

The large-trade feed lists recorded taker fills of $10,000 or more that meet its market-volume-share floor, marked BUY or SELL with the wallet's grade, live with Pro and 24 hours later without it. The sharp money guide walks through reading one game's wallets.

None of that is a signal to fade them. Across 46,857 large sports buys 0xinsider recorded from June 1 to September 11, 2026, D and F wallets came in -0.18 points against the price they paid, an interval from -1.73 to +1.36, and S, A and B wallets +0.50, from -0.58 to +1.59. Both include zero: a large MLB buy from a D wallet is no reason to take the other side, and one from an A wallet is no reason to follow it.