What Is Arbitrage Betting (Sure Bet)?

How a sure bet works

Every odd hides an “implied probability”: odds of 2.00 correspond to 1 ÷ 2.00 = 50%. If you add up the implied probabilities of all outcomes of an event and the total is less than 100%, an arbitrage exists: you can split your stake so that whichever outcome occurs, the return is greater than what you put in.

This usually happens because different bookmakers price the same event differently. One pushes up the favourite's odds, another the underdog's — and for a few seconds the two prices together leave a profit margin. Add betting exchanges (where you can lay, i.e. bet against an outcome) and the opportunities multiply.

Step-by-step example

A tennis match with two possible outcomes (Player A wins or Player B wins):

• Bookmaker X prices Player A at 2.04
• Bookmaker Y prices Player B at 2.02

Check: (1 ÷ 2.04) + (1 ÷ 2.02) = 0.490 + 0.495 = 0.985. Less than 1 → an arbitrage exists with a margin of ~1.5%.

Whoever wins, you get back €101.50 from the €100 you staked — a profit of €1.50 (1.5%), regardless of the score — provided both bets are placed at those odds.

How much do you actually win?

Realistic margins are 0.5%–3% per arbitrage. You won't get rich from a single bet; profit is built on frequency — dozens of small opportunities that appear and vanish within seconds. That's why speed is everything: by the time you work out the legs by hand, the odds have already moved.

What's the real risk?

Once every leg is placed, the match result doesn't concern you — there you're covered. The real risks are practical:

• Odds movement: if you place one leg but the price of the second changes, the margin can disappear.
• Account limits: bookmakers may limit players they consider consistently sharp.
• Voided bets: a bookmaker can cancel a bet it treats as a pricing error (a “palp”), leaving the other leg uncovered.
• Input errors: the wrong amount or the wrong market cancels your cover.

The guide to common arbitrage mistakes covers these risks and how to reduce them. You must also be 21 or older to bet in Greece.

How ArbPlay does this automatically

ArbPlay continuously scans odds across licensed Greek bookmakers, international betting exchanges and prediction markets, calculates arbitrages in real time and shows them to you ready to play — with the profit percentage and the links for each leg. You just place the bets before the opportunity disappears. No spreadsheets, no manual calculation.

The lay leg can sit on a betting exchange (Betfair, OrbitX) or a prediction market (Polymarket, Kalshi). Those two venue types work differently — different pricing, different fees, different currency — and ArbPlay does the arithmetic for whichever you pick.

If you have understood the maths and are now comparing tools rather than learning the mechanics, the buyer guide on choosing arbitrage software for Greek bookmakers sets out what to check.

Frequently asked questions

Is the profit in arbitrage betting really guaranteed?

Not in practice. On paper, covering every outcome at odds whose implied probabilities add up to less than 100% gives you the same profit whatever the result — provided every leg is placed at those odds. The real risk isn't the match result but execution: an odd can move before you place both legs, and a bookmaker can void a bet or limit your account.

How much do you win from an arbitrage?

Most arbitrages offer a 0.5%–3% margin on the total staked, if every leg is placed at the quoted odds. On a €100 stake that's €0.50–€3 profit. The money comes from volume and frequency, not from large percentages per bet.

Do I need a betting exchange for arbitrage?

Not always. An arbitrage can be made between two bookmakers (backing every outcome). Many opportunities, though, come from pairing a bookmaker with a betting exchange, where you lay (bet against) one outcome.

Related: Is it legal in Greece · Back & lay explained · How to calculate a sure bet · all guides.