The 2026 US Open tennis odds are really one question wearing three price tags: how healthy are the two best players in the world? Jannik Sinner has not hit a competitive ball since winning Wimbledon, withdrawing from both the Canadian Open and Cincinnati with a right knee problem. Carlos Alcaraz, the defending champion in New York, has not played a match since April because of a wrist injury. The prediction-market crowds on Kalshi and Polymarket have repriced both men hard. The sportsbook futures board, at least the one we pulled on August 18, has barely blinked. That disagreement is the whole story of this piece: we line up all three venues on the men's and women's winner markets, name by name, and show where each favorite is actually cheapest. Along the way you will meet one player a single venue prices at 6 cents while another venue does not list him at all.
The Quick Answer
On August 18, 2026, bet365's syndicated futures board priced Jannik Sinner at -150 to win the US Open, an implied 60%, while Kalshi traded him at 29-30 cents and Polymarket at 31-34 cents, a gap of nearly 30 probability points that reflects his knee injury and a competitive layoff that will reach seven weeks by the time the main draw starts. The exchanges are the cheaper place to back the injured favorites (Sinner, Alcaraz) and modestly cheaper on a healthy Aryna Sabalenka, while the sportsbook board is actually the better price on Alexander Zverev, Novak Djokovic, and Iga Swiatek. The full three-venue tables for both draws, and the one name Kalshi lists that Polymarket doesn't, are below.
Three Venues, Three Kinds Of Prices
A quick decoder before the tables, because the three venues quote the same opinion in different clothes. Kalshi and Polymarket are exchanges: a winner market is a YES/NO contract priced in cents, where 30 cents means the crowd's marginal trade puts the outcome at about 30%, and your cost above that is the bid-ask spread plus a trading fee. A sportsbook futures board quotes American odds with the operator's margin baked directly into the number: on the bet365 board we pulled, the five men it listed (Sinner, Alcaraz, Zverev, Djokovic, and Jack Draper, more on him later) sum to roughly 112% of implied probability all by themselves. If converting -150 into 60% is not second nature yet, our implied probability guide covers it, and the full Kalshi vs Polymarket comparison explains how these markets work mechanically. Here we only care about one thing: for each name, which of the three venues sells the same outcome for the least.
That question has a very different answer on the men's side than the women's, and the men's side is where the money disagrees most, so we start there.
The Men's Board: Two Injured Superstars, One Unmoved Book
All prices in this piece are as of August 18, 2026. Exchange prices are the YES bid/ask in cents; the sportsbook column is bet365's futures board as syndicated to VegasInsider that day, with its implied probability.
| Player | Kalshi (bid/ask) | Polymarket (bid/ask) | bet365 | bet365 implied |
|---|---|---|---|---|
| Jannik Sinner | 29¢ / 30¢ | 31¢ / 34¢ | -150 | 60.0% |
| Carlos Alcaraz | 19¢ / 20¢ | 18¢ / 20¢ | +187 | 34.8% |
| Alexander Zverev | 16¢ / 18¢ | 16¢ / 16.1¢ | +800 | 11.1% |
| Novak Djokovic | 7¢ / 8¢ | 6.7¢ / 9.1¢ | +11000 | 0.9% |
| Ben Shelton | 6¢ / 7¢ | 4.8¢ / 5.5¢ | not listed | — |
| Taylor Fritz | 4¢ / 5¢ | 4.1¢ / 4.6¢ | not listed | — |
The Sinner row is the loudest number on the page. Sixty percent at the book, about 30% on the exchanges. That is not a rounding disagreement; it is two different opinions about a knee. Sinner withdrew from Cincinnati saying his right knee "has been bothering me" and that he was "not ready to compete yet," after already skipping the Canadian Open, and reporting around his camp has him undergoing shockwave therapy in Turin before arriving in New York with under two weeks to train. The exchange crowds have traded that news down to a coin-flip-and-worse; Kalshi's Sinner market alone has done roughly 295,000 contracts. The book's -150 is the price of a healthy world No. 1, and if that is what Sinner turns out to be, the exchanges are giving away almost 30 points of probability. If it isn't, the book is. One of those two prices is significantly wrong, and that is precisely the kind of gap this comparison exists to surface.
Alcaraz is the same story with a longer timeline. The defending champion has not played since April's Barcelona Open because of wrist tenosynovitis, missed both Roland-Garros and Wimbledon, and is on the entry list without having formally confirmed he will play, though he has been building up practice loads. Both exchanges sell him at 18-20 cents; bet365 asks the equivalent of 34.8. Between the two injured stars, the book is charging about 95 combined points of probability for players the exchanges price at about 50 combined.
Now flip the direction, because the gap does not always favor the exchanges. Zverev, who won this year's French Open, trades at 16-18 cents on the exchanges but pays +800 at the book, an implied 11.1%. A Zverev backer gets a materially better price at the sportsbook, eight-to-one on a player the exchange crowd rates the clear third favorite and, on Kalshi, within a few cents of Alcaraz. Djokovic is even more extreme: +11000 at the book, under 1% implied, against 7-9 cents on both exchanges. Djokovic lost early in Cincinnati to Thiago Agustin Tirante and pointed afterward to "a lot of health issues," in his words, but he is expected in the field and is even entered in mixed doubles alongside Aryna Sabalenka. Whether you side with the book or the crowd on a 39-year-old chasing major No. 25, the venues are not close, and the gap is far too wide for both prices to be defensible.
Shopping the number is the whole game, on exchanges and off. OddsShopper's live tennis odds screen lines up every major sportsbook's price on the same match once US Open main-draw play begins, so you can spot when a book, Kalshi, or Polymarket is the one actually paying the most. New subscribers can try OddsShopper Pro free for 7 days, and code USOEXCH20 takes 20% off your first payment if you stay.
The Name One Board Doesn't Have
Here is the missing player promised at the top: Rafael Jodar. The 19-year-old Spaniard was ranked outside the world's top 500 twelve months ago, has charged to No. 11, and is in the middle of a Cincinnati run that includes saving a match point to beat Denis Shapovalov 7-5, 4-6, 7-5 from 1-5 down in the third set and then dismissing Alejandro Tabilo 6-2, 6-1 to reach the round of 16, where he faces Flavio Cobolli on August 19. Kalshi's crowd has made him a real US Open contender: 6-7 cents, with about 267,000 contracts traded and over 261,000 still open, more volume than the Djokovic market has done. Polymarket's men's winner market, which names 22 players plus a catch-all "Other" bucket (with zero volume traded) and a stack of unassigned placeholder slots, does not carry a Jodar contract at all, and he was nowhere on the sportsbook board we pulled either. When venues disagree this much about whether a player even belongs on the board, that is your reminder that these lists are curated at different speeds, and that the fastest-moving name in tennis can be tradable in one place and invisible in another.
The women's board has no Jodar and no injury cloud, which makes it the control group: this is what the three venues look like when they mostly agree.
The Women's Board: Smaller Gaps, Same Lesson
Same format, same August 18 pull.
| Player | Kalshi (bid/ask) | Polymarket (bid/ask) | bet365 | bet365 implied |
|---|---|---|---|---|
| Aryna Sabalenka | 24¢ / 25¢ | 25¢ / 26¢ | +225 | 30.8% |
| Iga Swiatek | 14¢ / 15¢ | 12¢ / 13¢ | +800 | 11.1% |
| Elena Rybakina | 10¢ / 11¢ | 9.5¢ / 9.9¢ | +800 | 11.1% |
| Coco Gauff | 8¢ / 9¢ | 8.8¢ / 8.9¢ | +700 | 12.5% |
| Naomi Osaka | 8¢ / 9¢ | 6.9¢ / 7.2¢ | +1000 | 9.1% |
| Mirra Andreeva | 7¢ / 8¢ | 6.8¢ / 6.9¢ | +1000 | 9.1% |
Sabalenka is the favorite everywhere, and the shape of her row is the normal one: exchanges at 24-26 cents, book at an implied 30.8%, a five-point premium that is mostly margin rather than disagreement. The interesting row is Swiatek. Fresh off winning the National Bank Open in Canada, she trades at 14-15 cents on Kalshi and 12-13 on Polymarket, both above the book's 11.1% implied at +800. Traders on both exchanges bought the Canadian title; the futures board hasn't. That makes Swiatek the clearest case on either draw where a believer should take the sportsbook price: eight-to-one at the book for a player the exchanges sell at 12-15 cents.
Gauff runs the other way. The book charges 12.5% implied at +700 while both exchanges sell her around 8.8-9 cents, a better than 10-to-1 price at the venues where actual traders set the number. And down the board, Polymarket is quietly the cheapest venue on Osaka, Rybakina, and Andreeva by half a cent to two cents over Kalshi. Small edges, but at these prices a cent or two is several percent of your potential payout.
SO Which Venue Is Cheapest?
Recall the Sinner row and run the same test down every name, and a clean pattern falls out of the tables. Exchanges are cheapest where the news is bad and recent: Sinner at 30 cents instead of 60, Alcaraz at 20 instead of 35, Sabalenka modestly cheaper too. The sportsbook is cheapest where the crowd has moved past it: Zverev at 8-to-1, Djokovic at 110-to-1, Swiatek at 8-to-1. Polymarket noses out Kalshi on most of the women's mid-board; Kalshi is the only venue that will sell you Jodar at any price. Nobody is cheapest everywhere, and that asymmetry is the point. Venue loyalty costs money; the reader who checks all three boards before backing a name gets an equal-or-better price than the reader who picked a favorite app in August and stopped looking.
A Worked Example: 100 Sinner Contracts ($100 Payout) At 30 Cents Vs -150
Numbers make the gap concrete. Buy 100 Sinner contracts on Kalshi at the 30-cent ask and you pay $30.00 plus a $1.47 taker fee (Kalshi's published formula: 0.07 × 100 contracts × 0.30 × 0.70), $31.47 all-in, for a $100.00 payout if he wins the title, a profit of $68.53. Put that same $31.47 on Sinner at bet365's -150 and a winning ticket profits $20.98. Identical opinion, identical stake, and the exchange pays more than three times as much, entirely because the two venues disagree about his knee. Polymarket's 34-cent ask lands between them. Run the same math on Zverev and it flips: 100 contracts at Kalshi's 18-cent ask cost $18.00 plus a $1.04 fee, profiting $80.96 on a win, while $19.04 at +800 profits $152.32. The venue that pays best changes row by row, and that flip is the entire argument for checking all three.
Two costs sit on top of these sticker prices, and they point in opposite directions. Exchange takers pay a trading fee on top of the ask (Kalshi and Polymarket calculate theirs differently), and both platforms quote a bid-ask spread that widens on longshots, while a sportsbook's cost is already inside the number you see. We walk through the exact formulas in our Kalshi and Polymarket fee breakdown and the standalone Kalshi fee guide; the short version is that fees narrow gaps of a cent or two, but they do not come close to closing a 30-point Sinner gap.
One honest caveat cuts the other way: a futures board syndicated at -150 is an advertised price, and books can be slow to refresh names they are not actively trading. Exhibit A is Jack Draper, listed at +2000 on the same bet365 board while both exchanges price him at a cent or less, for the sound reason that Draper, ranked 147th after arm injuries, missed the main-draw cut entirely and would have to come through qualifying, per Sky Sports. Treat any book price you cannot actually get down at as decoration. The exchange quote, whatever else you think of it, is a price someone will fill right now.
The Clock On All Of This
These numbers have a shelf life, and it is short. Qualifying runs August 24-28, the main draw starts Sunday, August 30, and the finals land September 12 (women) and September 13 (men). Between now and then come the draw itself, Sinner's first practice reports from New York, and an Alcaraz confirmation one way or the other, any of which can move a favorite five points in an afternoon. Our US Open men's model verdict tracks how an AI panel prices this same market against the Kalshi crowd, and Kalshi's own odds mechanics explain why exchange prices tend to move first: there is no trading desk to wait on, just the next order.
If you want to trade the exchange side of these gaps rather than just read about them, the Polymarket US App's current offer for new users is a $20 trading bonus after a $10 deposit and one qualifying trade (details in our Polymarket sign-up bonus guide), and prediction markets' legal footing state by state is covered in our are prediction markets legal explainer.
18+ Only. Restrictions and eligibility requirements apply. Not available in all jurisdictions. Trading is risky. 100% loss can occur. See polymarket.com/tos for more information. The Polymarket US App serves as an independent software provider and affiliate of Polymarket US and Polymarket Clearing, the CFTC-regulated exchange and clearing organization.
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FAQ: US Open Tennis Odds 2026
Why are Kalshi and Polymarket so much lower than sportsbooks on Sinner? Both exchanges repriced Sinner after he withdrew from the Canadian Open and Cincinnati with a right knee injury, leaving him no competitive matches between Wimbledon and the US Open. The bet365 futures board we pulled on August 18 still showed -150, an implied 60%, versus roughly 30% on the exchanges. The gap is a live disagreement about his fitness, not a quoting error.
Can US users trade US Open tennis winner markets? Yes, on both exchanges compared here: Kalshi is a CFTC-regulated exchange available to US users, and the Polymarket US App offers regulated US access to Polymarket markets. State-level eligibility differs, and the Polymarket offer excludes several states; the details are in our prediction markets legality guide.
When do these markets settle? The men's and women's winner markets settle when the finals are decided: the women's final is scheduled for September 12, 2026, and the men's for September 13, 2026, at Flushing Meadows.
The Bet Before The Bet
Start where this piece started: nobody actually knows what Sinner's knee or Alcaraz's wrist will allow over seven best-of-five (or best-of-three) matches in New York, and the venues are not pretending otherwise in unison. The book is charging you for the players these two were in June. The exchanges are charging you for the players the last six weeks suggest they might be. Whichever side of that argument you take, take it at the venue that prices your opinion cheapest, because the gap between venues is the one edge on this page that requires no medical opinion at all. Before any of it, check the free stuff: our free expert picks board is the no-cost place to see what our handicappers like as the draw takes shape.
