What is Arbitrage?

Arbitrage ("arbing") is placing bets on every possible outcome of an event, across different bookmakers, such that the combined prices guarantee a profit regardless of the result. It exploits pricing disagreements between books: when one bookmaker overprices one side and another overprices the other, the two prices together can leave no losing outcome. The test is the arbitrage percentage: sum the implied probabilities (1 divided by each decimal price). If the total falls below 100%, an arb exists and the gap is your margin. Worked example: a two-way market where Bookmaker A offers 2.10 on Player X and Bookmaker B offers 2.10 on Player Y. The implied probabilities are 1/2.10 + 1/2.10 = 0.476 + 0.476 = 0.952, or 95.2%. The 4.8% shortfall is the locked-in edge. Staking a total of £100 split evenly — £50 on each — returns £105 whichever player wins, a guaranteed £5 profit. With unequal prices you stake in inverse proportion to the odds so that every outcome returns the same amount. Why it matters: arbing is, in theory, risk-free profit independent of the result. In practice the margins are thin — typically 1% to 5% — so it demands large stakes, fast execution and meticulous accounting. Common pitfalls and caveats: prices move while you place the second leg, so a half-completed arb can leave you exposed; one bookmaker may void or limit a bet, breaking the cover; and stake limits cap how much you can earn. Crucially, bookmakers actively detect and restrict accounts that arb consistently, frequently slashing limits to a trivial sum. Arbing is legal but firmly unwelcome to operators. Compare to: Value Bet, Implied Probability, Vig.