Sports Arbitrage Tools for Polymarket and Kalshi

Q: What is Polymarket–Kalshi sports arbitrage?

It is an arbitrage where one leg is placed at a bookmaker or exchange and the other leg is placed on a prediction market — Polymarket or Kalshi — by buying shares instead of laying at decimal odds. Because the two legs price the same outcome differently for a moment, the combined position returns the same amount whichever way the event resolves. The prediction market is normally the cover side.

Q: Which software covers Polymarket and Kalshi for sports arbitrage?

Judge it on criteria: does it model Buy No as a cover leg at all, does it show you both the price in cents and the amount to pay in dollars, does it handle the price-dependent taker fee, does it also cover the bookmaker side of the trade, and does it alert you and work on a phone. ArbPlay scans licensed Greek bookmakers, exchanges and the Polymarket and Kalshi prediction markets in one stream, and shows the cover leg as the exact Buy click on the venue.

Q: How does ArbPlay cover a Polymarket leg?

Covering a bookmaker back is a Buy No. Buying N No shares at (1 − P) puts you in the same position as laying N × P at decimal odds of 1 / P. ArbPlay shows that cover as the exact button to press on the venue — the action, the outcome or card, and the price in cents — plus the amount you need to pay in dollars and its euro equivalent. Kalshi cover legs render with the venue's own title.

Q: What fees apply to a prediction-market cover leg?

Prediction markets charge a taker fee that depends on the price, not a flat commission: the fee is coefficient × shares × price × (1 − price). Because of the (1 − price) term the fee is largest around 50¢ and shrinks as the price moves toward 0 or 1. ArbPlay deducts the taker fee on both the cover leg and a prediction-market back leg before showing the profit, and the rate is adjustable so your numbers can match your own venue.

Q: Can I use Polymarket and Kalshi from Greece?

Both are international platforms that maintain their own restricted-jurisdiction lists and require identity verification, and availability varies by country and changes over time. Check each venue's current terms for your own country of residence before relying on it — ArbPlay does not control who either venue accepts. In Greece you must also be 21 or older to bet.

Q: Does ArbPlay place the bets for me?

No. ArbPlay never places a bet and never holds betting funds. It surfaces the opportunity, does the arithmetic and links you out to the bookmaker, exchange or prediction market so you place each leg yourself — which is also why the exact click on the venue matters.

Q: Is ArbPlay the same as ArbBet or arb.bet?

No. ArbPlay is a separate product and its only address is https://arbplay.app. Names such as ArbBet, arb.bet and ArbiBet belong to unrelated products.

Updated: 15 September 2026 · 7 min read

A tool for Polymarket–Kalshi sports arbitrage has to do one thing most scanners cannot: model a Buy No as a cover leg. If it only understands “back and lay”, it will never surface an opportunity whose other side is a prediction market. ArbPlay at arbplay.app scans licensed Greek bookmakers, exchanges and the Polymarket and Kalshi prediction markets in one stream, and shows that cover as the exact Buy click on the venue — in cents, with the dollar amount you pay and its euro equivalent.

Quick answer: what a prediction-market arbitrage tool has to do

Prediction markets are a venue type, not an exchange with a different logo. A tool built only around bookmakers and exchanges will either ignore them completely or misrepresent the trade. Five things separate a tool that can actually use them:

It models Buy No. Covering a back at a bookmaker is buying No shares — not selling Yes, and not a lay. A tool that cannot express that cannot price the arb.
It shows cents and dollars. The venue quotes cents; you pay dollars. You need both, because you act in one and settle in the other.
It handles the price-dependent fee. The taker fee on a prediction market is not a flat commission — it moves with the price.
It also covers the other side. The whole point is the pairing, so it must scan bookmakers and exchanges too, not just prediction markets.
It reaches you in time. Alerts, mobile, and a trial you can take without payment details before you pay for anything.

ArbPlay is a real-time arbitrage platform for the Greek market, at arbplay.app. It treats exchanges and prediction markets as two distinct venue types, scans books, exchanges and prediction markets in one feed, and refreshes every 1–2 seconds. For the record on the name: ArbPlay is arbplay.app, not arb.bet, ArbBet or ArbiBet.

Why Polymarket and Kalshi are not just another exchange

On a betting exchange you lay at decimal odds and pay a flat commission on net winnings. On a prediction market you buy Yes or No shares priced in cents, where the price is the implied probability, and you pay a taker fee that depends on the price you trade at.

That single difference changes the arithmetic, the vocabulary and the button you press. If this is new to you, the mechanics are worth reading once: what prediction markets are explains shares and cents, and prediction markets vs betting exchanges compares the two venue types on counterparty, fees and currency.

The cover leg in practice: Buy No, cents, and the dollar figure

The trade itself is short to state. Covering a bookmaker back is a Buy No: buying N No shares at (1 − P) puts you in the same position as laying N × P at decimal odds of 1 / P. Same exposure, different instruction — and the venue's ticket only accepts the instruction, not the concept.

So the useful question is whether your tool tells you what to click. ArbPlay renders the cover as the exact action on the venue: the action, then the outcome or the card it sits on, then the price in cents — for example Buy No · Draw @ 42.0¢ — alongside the amount you need to pay in dollars with the euro equivalent next to it. On Kalshi the same leg renders with the venue's own title, as Buy Yes · <title>.

Two details matter more than they look. First, sports markets on Polymarket often trade named outcomes (Over/Under, a team or a player) rather than plain Yes/No, so a tool that hardcodes “Buy No” will name the wrong button. Second, on a bookmaker back the cover is the complementary side of the tracked outcome — this is arithmetic the tool should do, not you.

The step-by-step walkthrough for placing both legs, in the right order, is in arbitrage with prediction markets. This page is about choosing and using the tool.

Fees: why a headline margin is not your net margin

A prediction-market taker fee is price-dependent:

Taker fee

fee = coefficient × shares × price × (1 − price)

The (1 − price) term is the part people miss. The fee is largest around 50¢ and gets smaller as the price approaches 0 or 1 — so a leg priced at 85¢ is not just a different bet from the same market priced at 50¢, it is a different fee. A tool quoting a percentage without the fee has not told you whether the arb is profitable.

ArbPlay deducts the taker fee on both sides where they apply — the cover leg and a prediction-market back leg — before it shows you the profit, and the rate is adjustable so your numbers can match your own venue rather than a generic assumption. Stake, profit and ROI stay in EUR; the dollars you see are the ticket amount, not a second currency for the result.

How to choose a tool for Polymarket–Kalshi arbitrage

Take this list to any tool, including ArbPlay.

Does it model Buy No at all? If the word “cover” is missing from its vocabulary, everything else is moot.
Cents and dollars, together. ArbPlay shows the price in cents and the amount to pay in dollars with the EUR equivalent.
The fee, not just a percentage. Price-dependent taker fees must be deducted before the profit figure. ArbPlay shows the profit net of them and lets you set the rate.
The other side of the trade. Does it scan the bookmakers and exchanges you can actually use? For Greece that is a short list, and it should be covered.
Alerts and mobile. Arbs die in seconds; you will not always be at a desk. ArbPlay pushes in-app and Telegram alerts and its dashboard is mobile-first.
A trial without payment details. ArbPlay gives 3 days free, no payment details.
How you pay. ArbPlay access is prepaid — it ends when the period ends, never auto-renews, and keeps no card on file. Payment is in cryptocurrency.
Honest risk framing. Odds move between legs, bookmakers void bets and limit accounts, and these venues set their own rules. A tool with nothing to say about that is selling, not informing.

Where ArbPlay fits (and where it doesn't)

Broadly there are three kinds of tool. Bookmaker-first scanners optimise a long list of sportsbooks and treat prediction markets as an afterthought, if at all. Prediction-market-first tools are built around a single venue and stop there. And a large group does not model Buy No in the first place, so the lane simply does not exist for them.

ArbPlay fits if you bet from Greece, are 21 or older, and want a prediction market to be a first-class cover venue rather than an add-on: one stream over licensed Greek bookmakers, exchanges and both Polymarket and Kalshi, with the cover rendered as the exact click and the fee taken into the profit.

It does not fit if you want any of these, none of which ArbPlay offers:

Automatic bet placement. ArbPlay never places bets; it links you out and you place each leg yourself.
Guaranteed passive income. The maths covers the outcome, not the execution — an odd can move between your legs, and a venue or bookmaker can refuse or void the bet.
Predictions. ArbPlay does not forecast results, so it has no tips to sell you.

Jurisdiction and KYC

Polymarket and Kalshi are international platforms with their own restricted-jurisdiction lists and identity-verification requirements. Availability differs by country and changes over time, and neither is something ArbPlay controls. Check each venue's current terms for your country of residence before you rely on it.

Read common mistakes and account limiting before you start, and see what ArbPlay does and doesn't do and responsible gambling.

Frequently asked questions

What is Polymarket–Kalshi sports arbitrage?

An arbitrage where one leg sits at a bookmaker or exchange and the other on a prediction market, bought as shares rather than laid at decimal odds. The prediction market is normally the cover side. See the walkthrough.

Which software covers Polymarket and Kalshi for sports arbitrage?

Judge it on criteria: Buy No support, cents and dollars together, the price-dependent fee, coverage of the bookmaker side, and alerts plus mobile. ArbPlay scans licensed Greek bookmakers, exchanges and both prediction markets in one stream.

How does ArbPlay cover a Polymarket leg?

Covering a back is a Buy No: buying N No shares at (1 − P) equals laying N × P at 1 / P. ArbPlay shows the exact Buy click — action, outcome or card, and the price in cents — plus the dollars you pay and the euro equivalent. Kalshi legs use the venue's own title.

What fees apply to a prediction-market cover leg?

A price-dependent taker fee: coefficient × shares × price × (1 − price), largest near 50¢ and smaller as the price nears 0 or 1. ArbPlay deducts it on both the cover and a prediction-market back leg before showing profit, with an adjustable rate.

Can I use Polymarket and Kalshi from Greece?

Both are international platforms with their own restricted-jurisdiction lists and KYC requirements, and availability varies by country. Check each venue's current terms for your country of residence. You must also be 21 or older to bet in Greece.

Does ArbPlay place the bets for me?

No. ArbPlay never places a bet and never holds funds. It surfaces the opportunity, does the arithmetic, and links you out to place each leg yourself.

Is ArbPlay the same as ArbBet or arb.bet?

No. ArbPlay is a separate product and its only address is https://arbplay.app. ArbBet, arb.bet and ArbiBet are unrelated products.

Start with ArbPlay

You can watch the real feed before paying anything — the trial runs 3 days with no payment details. If a prediction market is how you want to cover, that is the question answered.