How to bet on tennis on Kalshi and Polymarket: match winners, set and game spreads, retirements and fees

Tennis is now one of the busiest sports on the prediction markets. On Kalshi, the ATP match between Ben Shelton and Carlos Alcaraz on 8 November traded more than 6 million contracts across its two sides. On Polymarket, an ordinary tour match such as James Duckworth v Cameron Norrie at the Stockholm tournament on 9 November had ten separate markets and nearly $290,000 of trading.

Tennis suits exchanges well. Matches happen every day for most of the year, there are only two outcomes, and prices move point by point. This guide explains which markets you can trade, how they settle, the rules that matter most in tennis (retirements and walkovers), what it costs, and how to place a trade.

The short version

• Where: Kalshi, regulated in the US, lists ATP and WTA match winners and a growing range of other tennis markets. Polymarket lists ATP and WTA matches with up to ten markets each, outside the US.
• What you buy: a contract that pays $1 if your player wins. A price of 69¢ means the market gives that player about a 69% chance.
• The rule to read first: what happens if a player retires mid-match or withdraws before it starts. The two platforms treat a walkover differently.
• What it costs: a fee only when you take a price that is already on the book, largest at 50¢ and smallest near 0 or $1.

Where you can trade tennis

Kalshi is regulated by the CFTC and open in most US states. It lists ATP match winners in its “ATP Tennis Match” series, WTA matches, Challenger matches, doubles, and markets on tournament winners, sets, games, aces and who qualifies for the ATP Finals. If you are new to it, start with our Kalshi review.

Polymarket lists ATP and WTA matches, often with a full set of markets on each. Its main exchange is not open to US residents; in the US it runs a separate CFTC-regulated app with a narrower list (how to use Polymarket in the US).

Both settle on the official result from the tour. Kalshi names the ATP website as its source for ATP matches; Polymarket names official ATP Tour information, backed by credible reporting.

Every tennis market type, explained

• Match winner. The main market, and where almost all the money is. On the Duckworth v Norrie match, it took $281,939 of the $289,608 traded.
• Set winner. Who wins the first set, or a given set. Useful if you think a player starts fast or tires.
• Total sets. Over or under 2.5 sets in a best-of-three: a bet on whether the match goes to a decider.
• Total games. Over or under a number of games, such as 22.5. Close matches with tie-breaks go over; one-sided ones stay under.
• Set handicap. For example, Norrie -1.5 sets: he must win in straight sets.
• Game spread. For example, Norrie -3.5 games: he must win at least four more games than his opponent across the match.
• Completed match. Yes if the match is played to a finish; a retirement, walkover or cancellation makes it No.
• Tournament winner. Who wins the event, often listed before the draw.
• Qualification markets. For example, Kalshi’s and Polymarket’s markets on which players qualify for the ATP Finals.

On Kalshi you will also find game winner markets within a set, aces, game spreads and markets on whether a player wins a tournament without dropping a set.

How a tennis market works

Each market is a question with a Yes and a No side. If you buy Yes on “Tomas Machac wins” at 69¢ and Machac wins, each contract pays $1, a profit of 31¢ before fees. If he loses, you lose the 69¢.

Prices move during the match. You can sell at the current price at any point, including between sets (how to sell shares early). Two things differ from a sportsbook:

1. You trade with other people. The price is wherever buyers and sellers meet, and you can post your own price as a limit order (limit order v market order).
2. There is no house margin in the price. On a sportsbook, the implied chances of the two players add up to more than 100%. On an exchange, Yes for one player and Yes for the other add up to about $1; your cost is the fee and the spread (reading odds).

Retirements, walkovers and delays: the rules that matter

Tennis has a problem most sports do not: a player can retire halfway through a match, or withdraw before it starts. The two platforms handle this differently, and it can decide whether you are paid.

• Polymarket: the market resolves to the player who advances. If the match starts and one player retires, defaults or is disqualified, the player who advances wins the market. If the match ends in a walkover (a withdrawal before the start), it settles 50-50. If the match is cancelled, ends in a tie, or has no winner within 14 days of the scheduled start, it also settles 50-50.
• Kalshi: the market resolves to the player who wins the match “after a ball has been played”. If the match never starts because of an injury, walkover, forfeit or cancellation, Kalshi settles it at a fair price under its rules, not automatically 50-50. If the match is postponed or delayed, the market stays open and closes after the rescheduled match, within two weeks.

In practice: if you back a player who is clearly injured, a mid-match retirement settles the match market against you on both platforms. Some markets, such as set and game markets, depend on whether the set or match is completed; read each market’s rules before you trade (how to read market rules).

What it costs: fees and spreads

Both platforms charge a fee only when you take a price that is already on the book.

• Polymarket: tennis markets carry the sports fee of 5% × price × (1 − price) per share, charged to takers only. At 50¢ that is 1.25¢ a share; at 69¢ about 1.07¢; at 90¢ 0.45¢. Makers pay nothing and part of the fee is paid back to them as a rebate.
• Kalshi: the standard taker fee is 7% × price × (1 − price) per contract, rounded up to the cent on each order. ATP match markets are on Kalshi’s schedule with maker fees, so a resting order that fills pays a quarter of the taker rate (Kalshi fees).

The other cost is the spread. On busy tour-level matches on Kalshi it is often 1¢. On Challenger matches and small side markets it can be several cents. On the Sonego v Halys match on Kalshi on 9 November, for example, Halys was bid at 53¢ and offered at 56¢, a 3¢ gap, with only a few hundred contracts traded.

Live examples this week

On Kalshi on 9 November, the ATP list included:

• Tomas Machac v Borna Gojo, Stockholm: Machac 69¢, Gojo 30¢, with about 196,000 contracts traded.
• Ugo Humbert v Adolfo Daniel Vallejo: Humbert 65¢, Vallejo 37¢.
• Holger Rune v Zizou Bergs: Rune 60¢, Bergs 42¢.

Prices are the last trades, so the two sides can add up to slightly more or less than $1.

ATP Finals qualification. Kalshi’s market on who qualifies for the season-ending ATP Finals had seven players at 99¢: Carlos Alcaraz, Jannik Sinner, Alexander Zverev, Arthur Fils, Ben Shelton, Daniil Medvedev and Frances Tiafoe. For the last place, Alex de Minaur was 7¢, Taylor Fritz 2¢ and Novak Djokovic 2¢. Polymarket’s version had de Minaur at 6.9¢ and Fritz at 2.25¢. Live prices: Kalshi’s qualifiers market and Polymarket’s.

Which matches have enough liquidity

Volume varies a lot from match to match, and it decides how easily you can get in and out. On Kalshi, the ATP matches on 8 November ranged from about 450,000 contracts across both sides for Alex Michelsen v Yannick Hanfmann to 1.8 million for Adrian Mannarino v Toby Samuel and 6.2 million for Shelton v Alcaraz. A match between two well-known players draws far more trading than an early-round match, and the gap between bid and ask is usually tighter as a result.

Two habits help. Check the volume and the order book before you trade, not only the price (how to read an order book). And on a quiet match, post a limit order and wait rather than paying a wide spread: crossing a 3¢ spread on a 50¢ contract costs more than the taker fee on either platform (1.25¢ on Polymarket, about 1.75¢ on Kalshi).

How to think about a tennis price

• Form and surface. Tennis results depend on the court. A player who is strong on clay can be weaker on a fast hard court, so check how each player has done on the surface being played.
• Fitness and schedule. Late in the season, players are tired and some are managing injuries. A retirement settles against the player who retires, so a doubt about fitness matters more than in many sports.
• Best of three v best of five. Most tour events are best of three sets, which gives the underdog more room than a best-of-five men’s Grand Slam match.
• Markets move fast in play. A single break of serve can move the price a long way. If you trade during a match, use limit orders and expect a delay between the point and the price.

Before you trade, write down your own probability, compare it with the price and only buy if the difference covers the fee and spread (how to calculate expected value). Size each trade so that a run of losses does not hurt (Kelly criterion).

How to place a tennis trade, step by step

1. Open the match on Kalshi or Polymarket and check the tournament, the scheduled time and the rules.
2. Decide the market: match winner for a simple view, sets or games for a view on how the match goes.
3. Check the spread. If it is more than a cent or two, use a limit order at your price.
4. Enter the number of contracts and confirm. The most you can lose is what you paid.
5. Follow the match. You can sell at any time if the price moves your way, or hold to the end.

For other sports on the same platforms, see our sports prediction markets guide and how to bet on the NBA.

Prices as of 9 November 2026. Prediction markets carry a real risk of loss, and nothing here is financial advice.