Surebets (Arbitrage Betting) Explained: How They Work and Why They Are Not Risk-Free
Updated 2026-10-036 min read
A surebet, or arbitrage bet, happens when the best odds you can find at different bookmakers are so far apart that covering every outcome guarantees a profit. The maths is simple and exact. The practice is harder, and this guide covers both.
The condition for an arbitrage
Take the best decimal odds for each outcome across bookmakers, convert each to 1 / odds and add them up. If the total is below 100%, there is an arbitrage.
Arbitrage if Σ(1 / best odds) < 1. Guaranteed profit = 1 ÷ Σ(1 / odds) − 1. Stake on each outcome = total stake × (1 / its odds) ÷ Σ(1 / odds).
A worked example
A tennis match with two outcomes. Bookmaker A offers 2.10 on player 1. Bookmaker B offers 2.05 on player 2. The sum is 1/2.10 + 1/2.05 = 47.6% + 48.8% = 96.4%, below 100%.
With a total stake of 100: put 49.40 on player 1 and 50.60 on player 2. If player 1 wins you get 49.40 × 2.10 = 103.74; if player 2 wins you get 50.60 × 2.05 = 103.73. About 103.73 either way, a profit of about 3.73% whatever the result.
Enter the best odds you found for each outcome (at different bookmakers).
Illustrative calculator. Results depend entirely on the numbers you enter.
Switch to three outcomes to see a football 1X2 case. The default example (3.10 / 3.60 / 2.55) adds up to 99.25%, a thin 0.75% profit. In practice most 1X2 markets add up to well over 100% because of the bookmaker margin, so real opportunities are rare and short-lived.
Why it is not risk-free in practice
- Odds move while you place the second bet. If the first leg is taken and the second price disappears, you are left with an ordinary bet.
- Rules differ between bookmakers: a match abandoned, a retired player or a different settlement rule can void one leg and not the other.
- Mistakes in the odds are a common source of apparent surebets, and bookmakers can cancel bets placed at obviously wrong prices.
- Bookmakers limit or close accounts that win consistently through arbitrage.
- Funds are tied up in several accounts, and withdrawal rules and fees can eat a thin margin.
A surebet is only guaranteed on paper. Margins are small, so every cost and every mistake matters. Never stake money you cannot afford to lose, and check each bookmaker's rules before you place any bet.
Frequently asked questions
What is a surebet?
A set of bets on every outcome of an event, placed at different bookmakers at odds high enough that the result is a profit whichever outcome happens.
How do you calculate an arbitrage bet?
Add up 1 divided by the best odds of each outcome. If the sum is below 1, there is an arbitrage, and the profit is 1 divided by the sum, minus 1.
Are surebets really risk-free?
Only on paper. Odds can change between bets, rules can void one side, and bookmakers may cancel mistaken prices or limit your account.
Why are real surebets so rare?
Bookmakers build a margin into every market and correct price differences quickly, so the combined best odds rarely add up to less than 100%.
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