What Is Arbitrage Betting (Sure Bet)?
Arbitrage betting (or a “sure bet”) means betting on every possible outcome of an event — across different bookmakers or on a betting exchange — at odds that guarantee a profit no matter who wins. It isn't a prediction. It's mathematics.
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.
The rule
An arbitrage exists when: (1 / odds₁) + (1 / odds₂) + … < 1
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%.
With €100 of capital
You split the stake in proportion to the probabilities:
→ €49.76 on Player A @ 2.04 = return €101.50
→ €50.24 on Player B @ 2.02 = return €101.50
Whoever wins, you get back €101.50 from the €100 you staked — a guaranteed profit of €1.50 (1.5%), regardless of the score.
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, certain 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?
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.
- Input errors: the wrong amount or the wrong market cancels your cover.
You must also be 21 or older to bet in Greece.
How ArbPlay does this automatically
ArbPlay continuously scans odds across licensed Greek bookmakers and international betting exchanges, calculates arbitrages every 1–2 seconds 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.
Related: the full guide series — legality, back/lay exchanges, calculating a sure bet and more — is available now in Greek under Οδηγοί, with English versions on the way. See all guides.