How arbitrage works
Every decimal price hides an implied probability, equal to its inverse. At a single bookmaker, the sum always exceeds 100%: that is its margin. But by taking the best odds for each outcome at different bookmakers, the sum can fall below 100%. The gap is your guaranteed profit.
The stakes are split in proportion to the inverse of each price: stake on outcome i = total × (1/cᵢ) / Σ(1/cⱼ). Every outcome then returns exactly the same amount. The profit is 1 / Σ(1/cⱼ) − 1 of the total stake.
Example
A tennis player priced 2.10 at one bookmaker, their opponent 2.05 at another. Sum of the inverses: 0.476 + 0.488 = 0.964. On €100: €49.40 on the first and €50.60 on the second. Whoever wins, you collect €103.70: +3.7%, guaranteed.
Frequently asked questions
Are surebets really risk-free?
On paper, yes; in practice, four things go wrong: the odds move between your two bets, a bet is voided under rules that differ from one bookmaker to another, an obviously wrong price is cancelled after the fact, and above all mainstream bookmakers limit arbers' accounts. Read our guide on surebets before you start.
Where can I find surebets?
They appear when bookmakers don't align at the same speed, so mostly in the minutes after a market move. Proba Bet detects them automatically by reading nearly 30 bookmakers every 45 seconds; the Risk-free combinations tab on the dashboard shows them with the stake split.
Arbitrage or value betting?
A surebet is the meeting of two bets, at least one of which is a value bet. Covering both sides guarantees 1 to 3% but doubles the stakes and attracts limits; playing only the side with value gives a far higher expectation, with variance. Arbitrage is the school; value betting is the trade.