How to Arbitrage Polymarket and Kalshi vs Sportsbooks
Polymarket and Kalshi vs sportsbooks step by step: share price to odds, taker fees with dates, the order book, where each exchange works, 30 days of data.
Contents
Arbitrage between Polymarket or Kalshi and a sportsbook means buying shares on one outcome on a prediction market and betting the opposite outcome at a sportsbook, when the share price including the exchange fee and the sportsbook odds give a sum of inverse odds below one. As in any arbitrage betting, the order is always the same: find the gap, subtract the exchange's taker fee, check the order book, and only then place both legs. The fee is charged per trade, not on profit, and depends on the share price.
Over 30 days, from October 6 to November 5, 2026, the Dozor scanner recorded 438,206 surebet episodes involving Polymarket and 82,508 involving Kalshi; across all books there were 4,829,879 episodes and 1,397,673 distinct surebets. A surebet with an exchange has the same 2-second median lifetime, but 7.5% of surebets with Polymarket and 6.4% with Kalshi last over a minute, versus 3.9% across all books. Methodology.
Share price and odds
On an exchange an outcome trades in shares: a winning share pays $1, a losing one pays 0. The share price is the market's probability estimate, and the odds before fees equal 1 / price: 0.45 is 2.22, 0.52 is 1.923. You can convert a price into odds and back in the odds converter.
The taker fee is paid on top of the price, so a share's real odds are lower: k′ = 1 / (price × (1 + r × (1 − price))), where r is the fee rate. On Polymarket sports markets r = 0.05: a share at 46¢ gives k′ = 2.117 instead of 2.174.
Four steps
| Step | What you do | The number you decide on |
|---|---|---|
| 1. Find the gap | compare the share price with the sportsbook's odds | sum of inverse odds below 1 |
| 2. Subtract the fee | work out the share's k′ with the taker fee | ROI after the fee |
| 3. Check the order book | see how many shares sit at the surebet price | depth in dollars vs the leg size |
| 4. Execute | buy shares at the price you calculated from and bet at the sportsbook | fill price |
A limit order that doesn't fill at once and rests in the book is a maker order: on Polymarket makers pay no fee. A market order fills immediately and pays the taker fee.
Fees
| Venue | Taker fee | Rate | Maker | Source |
|---|---|---|---|---|
| Polymarket | shares × r × price × (1 − price) | sports, economics, culture, weather, other — 0.05; crypto — 0.07; finance, politics, tech — 0.04; geopolitics — 0; combos — 0.05 | 0 | Polymarket docs |
| Polymarket US (separate US platform) | Θ × contracts × price × (1 − price) | Θ = 0.0695, table tennis 0.10, since October 28, 2026 | rebate by volume tier | Polymarket US docs |
| Kalshi | model fee per contract | in the API docs example: 0.07 × price × (1 − price) | some series charge makers too | Kalshi docs and help center |
Checked on November 5, 2026. Polymarket fees are calculated in dollars and rounded to 5 decimals; Kalshi rounds the fee up to $0.000001 and aligns the balance to $0.0001 for direct members or to a cent for customers of a broker (FCM). Polymarket itself charges nothing to deposit or withdraw, but deposit services such as Coinbase or MoonPay may charge their own fees; Polymarket's trading collateral is pUSD, a token on Polygon backed by USDC: deposits in USDC and USDC.e are wrapped into pUSD.
Break-even: how much the fee takes at different share prices.
| Share price | Polymarket, sports | Polymarket US | Kalshi (0.07) |
|---|---|---|---|
| 10¢ | 4.5% | 6.3% | 6.3% |
| 30¢ | 3.5% | 4.9% | 4.9% |
| 50¢ | 2.5% | 3.5% | 3.5% |
| 70¢ | 1.5% | 2.1% | 2.1% |
| 90¢ | 0.5% | 0.7% | 0.7% |
The percentage is of the amount spent on shares: the fee equals r × (1 − price). The gap on the exchange leg has to cover this before the surebet makes anything; the more expensive the share, the smaller the fee in percent.
Examples
Polymarket vs a sportsbook. CS2: a "MOUZ (−1.5)" share on Polymarket at 46¢, a sportsbook offers 2.05 on "G2 (+1.5)", budget $500.
| Without the fee | With the fee | |
|---|---|---|
| Share odds | 2.174 | 2.117 |
| ROI | 5.51% | 4.14% |
| Stakes | 520.71 shares for $245.99 (fee $6.47) and $254.01 at the sportsbook | |
| Profit on any outcome | $20.71 |
Kalshi vs a sportsbook. YES on Kalshi at 45¢, a sportsbook offers 2.05 on the opposite outcome, budget up to $500, whole contracts: 523 contracts for $244.42 (fee $9.07, rounded up to the cent) and $255.12 at the sportsbook, $499.54 in total. The contract's odds after the fee are 2.140, the ROI is 4.70%, the worst-case profit is $23.46.
You can run such a surebet in the Polymarket arbitrage calculator or in the arbitrage calculator with the "Exchange ¢" leg type: it takes the price in cents, the venue and the market category and adds the fee itself — details in How to Calculate Arbitrage Bets.
What the data showed
| Exchange | Episodes | Median lifetime | Over 60 s | Prematch | Main markets |
|---|---|---|---|---|---|
| Polymarket | 438,206 | 2 s | 7.5% | 15.5% | winner — 77%, handicap, total |
| Kalshi | 82,508 | 2 s | 6.4% | 19.6% | winner — 97.5%, total |
| Pair | Episodes | Median lifetime | Over 60 s |
|---|---|---|---|
| Duel — Polymarket | 59,517 | 2.1 s | 12.0% |
| 1xBet — Polymarket | 59,329 | 2 s | 4.7% |
| GGBet — Polymarket | 18,793 | 4 s | 14.3% |
| CSGOPositive — Polymarket | 15,924 | 4 s | 13.1% |
| Thunderpick — Polymarket | 12,342 | 2 s | 8.2% |
| 1xBet — Kalshi | 10,775 | 2 s | 4.9% |
| Duel — Kalshi | 10,456 | 2 s | 6.8% |
The table covers pairs with international sportsbooks. What it means: surebets with exchanges appear as fast as those between sportsbooks, but last a minute noticeably more often, especially in pairs with GGBet, CSGOPositive and Duel. 64% of Polymarket surebets are CS2, then Dota 2 (93,130). The GGBet, CSGOPositive and Thunderpick pairs with Polymarket and the Kalshi pairs come from a query to the same history over the same window.
What breaks the arbitrage
- Settlement rules. An exchange market is defined in text. On Polymarket esports markets, a canceled match or one postponed by more than 14 days settles 50-50, while at a sportsbook a canceled match often means a void bet — at Pinnacle, for example, a match not started within 30 hours is void; in the example above that turns a $20.71 profit into $14.36.
- The order book. Only a limited volume sits at the surebet price. The rest of the order fills at a worse price and the ROI is gone, so the leg must not be larger than the depth.
- The second leg. If the sportsbook bet doesn't go through — for example, it runs into the book's betting limits — you hold a position on the exchange. You can sell it before the match ends at the current price — with the fee and the spread.
- Deposits and withdrawals. Money on the exchange sits in the pUSD collateral token, at the sportsbook in the account currency. Exchange rates and deposit and withdrawal fees are part of the calculation; details in the article on Polymarket fees and withdrawals.
Where the exchanges are available
Facts from the venues' own rules only; this is not legal advice. What the law says in the US, the UK, Canada and Australia is in Is arbitrage betting legal?
- Polymarket. Its official restriction list (Polymarket help center, updated October 29, 2026) has 40 countries, including the US, the UK, France and Australia, plus four Canadian provinces: Ontario, Alberta, British Columbia and Quebec. Access depends on physical location, not residency; the help center explicitly prohibits using a VPN or similar tools to access Polymarket from these countries, as a violation of the Terms of Service (section 2.1.4). For the US there is a separate regulated platform, Polymarket US.
- Kalshi. Kalshi is a CFTC-regulated exchange. It operates in the US and in many other countries under its member agreement; residents of restricted jurisdictions — including the UK, Canada and Australia — may not trade event contracts (section VI, version of October 1, 2026).
How it works in Dozor
Polymarket and Kalshi are connected like any other book: their markets are mapped to the same types as sportsbook markets and take part in the surebet search on equal terms. Surebet ROI with exchanges is net of the taker fee. The "Exchange order book depth from, $" filter hides surebets with little volume at the best price. Overview on the prediction markets page.
FAQ
Does Polymarket take a fee on profit?
No: the taker fee is charged per trade, when you buy, and depends on the share price — shares × 0.05 × price × (1 − price) on sports markets. Makers pay nothing.
Are there surebets between Polymarket and Kalshi?
Yes, but rarely: 2,253 episodes in 30 days, 26 times fewer than the Duel — Polymarket pair. Both exchanges charge a fee, so the price gap has to cover it: YES at 45¢ on Polymarket and NO at 50¢ on Kalshi give 2.05% after fees, while 48¢ and 49¢ give almost nothing, 0.003%.
Can I sell shares before the match ends?
Yes, that is a difference between an exchange and a bet: you can close the position at the current price, with the fee and the spread.
Where do the fee numbers come from?
From Polymarket and Polymarket US documentation and from Kalshi's documentation and help center as of November 5, 2026 — links below. Check the primary source before trading: rates change.
Sources
Checked on November 5, 2026.
- Polymarket fees: formula, rates by category, rounding, free deposits and withdrawals.
- Polymarket US fees: Θ = 0.0695 since October 28, 2026, 10:00 PM ET; what Polymarket US is.
- Polymarket collateral, pUSD and deposits: USDC and USDC.e are wrapped into pUSD.
- Kalshi fee rounding: the model fee example 0.07 × 0.055 × 0.945, rounding and balance alignment; Kalshi help on fees (April 19, 2026).
- Polymarket geographic restrictions, updated October 29, 2026; geoblock documentation.
- Trading on Kalshi from outside the US (March 20, 2026), how Kalshi is regulated and the Kalshi member agreement, section VI, version of October 1, 2026.
- Polymarket "Map Handicap" market rules: 50-50 on cancellation or a postponement beyond 14 days.
- Dozor: data — methodology.
What next
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