Polymarket odds explained: how to use it, and how Kalshi compares

Polymarket odds are prices. Each player in a tennis match has a price between 1¢ and 99¢, that price is the market's estimate of their chance of winning, and a share pays $1 if they win and nothing if they lose. A player at 62¢ is being given a 62% chance. That one idea covers most of what people ask about Polymarket, and this guide fills in the rest: how to use the site, what it costs, how its tennis markets settle, how it compares with Kalshi, and what the ATP partnership changed. Every fact below comes from Polymarket's or Kalshi's own pages, checked on 31 October 2026.

What a Polymarket price means

Polymarket's own help page puts it in three words: "Prices = Probabilities." A yes share priced at 18¢ implies an 18% chance. Prices are set by the people trading, not by Polymarket, and the person on the other side of your trade is another user, not the platform. That's the main difference from a bookmaker, which sets its own odds and takes the other side itself.

Each pair of shares, one for each player, is backed by $1. When the match ends, the winning side pays $1 a share and the losing side pays nothing. You don't have to wait for that: the help page says you can sell your shares at any time at the current market price. Because exactly one player wins, the two prices add up to about $1. If one player is 62¢, the other is about 38¢. For the longer version of why a price and a probability are the same thing, read how tennis prices work. To turn a Polymarket price into decimal, fractional or American odds, use the odds converter.

How to use Polymarket, in five steps

1. Open an account and add money. Balances are held in USDC, a dollar token. Polymarket's fee page says it charges nothing to deposit or withdraw USDC, though a card provider or exchange you use to get the money there may charge its own fee. How you fund it depends on where you live, so follow Polymarket's own instructions for that part.
2. Find the match. Tennis sits under sports. Search for a player's surname and check the tournament and start time in the market description, because the same two players can meet more than once in a season.
3. Choose an order type. Polymarket's trading documentation describes two kinds. A limit order names your price and can rest on the book until it fills, expires or you cancel it. A market order takes the best price available right now and never rests: any amount that can't fill is cancelled. Only orders that take liquidity pay a fee.
4. Mind the minimums. Each market has its own minimum order size, in shares. On the live ATP match markets I checked through Polymarket's public API on 31 October 2026, the minimum was 5 shares and prices moved in steps of 1¢, with some markets at a tenth of a cent.
5. Sell during the match, or hold to the end. Selling locks in whatever the price is now. Holding means your shares settle at $1 or $0 when the market resolves. The step-by-step guide walks through a first trade with screenshots in words.

What Polymarket charges

You pay a fee only when your order fills straight away against the order book. On sports markets the fee is shares × 5% × price × (1 minus price), which comes to $1.25 on 100 shares at 50¢ and shrinks toward either end of the price range. Orders that rest on the book pay nothing. Polymarket's fee page states plainly that makers are never charged fees. Other categories use rates from 4% to 7%, and geopolitics markets have no fee. The full table, with worked examples and the effect on your break-even price, is in Polymarket fees explained.

How Polymarket's tennis markets settle

Every tennis market carries its own rules text. The live ATP match markets I read on 31 October 2026 all used the same wording, in four parts:

• The market resolves to the player who advances.
• If the match begins but isn't completed, and one player advances because the other retires, defaults or is disqualified, the market resolves to the player who advances. One point played is enough.
• If the match ends in a walkover, meaning a player withdraws before the start, the market resolves 50-50: every share pays 50¢.
• If the match is cancelled, ends in a tie, or has no winner within 14 days of the scheduled start, the market also resolves 50-50.

The primary source is official information from the ATP Tour, with a consensus of credible reporting as a fallback. The practical point is the gap between a retirement and a walkover: a favourite you bought at 85¢ pays $1 if the opponent retires after one point, and 50¢ if the opponent pulls out before the first ball. What happens if a player retires covers the trading side of that.

Polymarket vs Kalshi for tennis

Kalshi is a US exchange that also lists ATP and WTA match markets. Here is how the two compare on the things that matter for a tennis trade, using only what their own pages say.

Two differences stand out. First, fees: at 50¢ a Kalshi taker pays up to 1.75¢ a contract and a resting order still pays something, while a Polymarket taker pays 1.25¢ a share and a resting order pays nothing. Second, walkovers: Polymarket pays 50¢ a share, Kalshi pays a "fair price" by its rules. Whether you can use either depends on where you live, and neither this page nor I can tell you that. Read their pages for your own situation.

What the ATP partnership changed

On 3 August 2026 Polymarket announced, in a press release, that it had become the Official Prediction Market Provider of the ATP Tour. The deal, with Tennis Data Innovations, the joint venture that manages the ATP's data and streaming rights, gives Polymarket exclusive streaming rights for ATP Tour and ATP Challenger Tour matches within the prediction market category: about 20,000 matches a season, qualifying and doubles included. Sportradar, as the ATP's distribution partner, supplies official real-time data and odds for settlement, and its integrity services cover Polymarket's ATP markets. The release says registered Polymarket users in the US can watch live matches alongside the related markets.

For a trader the useful parts are the data and the settlement source: the score the market sees is the official one, and settlement from an official feed means fewer disputes about who advanced. Watching the match inside the app is a convenience. It doesn't change the prices, the fees or the rules above.

Is there a Polymarket strategy for tennis?

Not a secret one. The price is the crowd's best guess, and the only way to beat it is to know something about the match that the crowd has priced wrongly. In tennis the biggest price moves come from breaks of serve, tiebreaks and the deciding set, so most useful approaches are about when to buy and sell around those, with a plan for getting out. The strategies hub sets them out with real numbers, and the win-chance calculator gives you a model price to compare with the market's.

Sources

All checked on 31 October 2026: Polymarket's help article What is Polymarket for prices, payouts and selling at any time; Polymarket's fee page for the formula, the rates, maker and taker treatment and deposits; Polymarket's order documentation for limit and market orders and minimum sizes; the rules text, minimum order size and fee flags of live ATP match markets from Polymarket's public API; Polymarket's Terms of Use for restricted territories; Polymarket's press release of 3 August 2026 on the ATP Tour partnership; Kalshi's fee schedule page; Kalshi's sign-up help page; and the rules text and settlement source of Kalshi's ATP match series from Kalshi's public API. Where this page and those pages disagree, those pages win.

FAQ

Are Polymarket odds the same as betting odds?

They carry the same information in a different form. A Polymarket price of 62¢ is a 62% chance, which is decimal odds of 1.61 or American odds of -163. The difference is that the price is set by other traders, the two sides add up to about $1, and you can sell before the match ends.

Can I use Polymarket in the United States?

Polymarket's Terms of Use list the United States among the territories where trading on polymarket.com is not permitted, and the site directs US users to Polymarket US, which Polymarket describes as a CFTC-regulated designated contract market. Check Polymarket's own pages for your situation; this page doesn't give legal advice.

Does Kalshi have tennis markets?

Yes. Kalshi lists an ATP tennis match series with the ATP as its settlement source, and WTA match markets too. Its fee schedule page shows taker fees of $0.07 to $1.75 per 100 contracts, plus maker fees on the ATP series.

What happens on Polymarket if a player retires?

If the match has started, the player who advances wins the market, even after a single point. If a player withdraws before the start, that's a walkover and the market resolves 50-50, with every share paying 50¢.

What did the Polymarket and ATP deal change for traders?

Official ATP data and odds from Sportradar now feed the markets and their settlement, and registered US users can watch ATP matches inside the app. The prices, fees and resolution rules work the same way as before.