What is a Sure Bet?

A sure bet (or arbitrage bet, also called an "arb") is a situation where you back all possible outcomes of an event at different bookmakers, and the combined odds guarantee a profit regardless of the result. When bookmakers disagree on the price of an event — even temporarily — a mathematical window exists where backing all outcomes locks in a risk-free return.

Sure bets are rare and short-lived. Bookmakers monitor each other's prices and adjust quickly. However, they occur most frequently around breaking news (team injuries, late lineup changes), at market opening, and in less liquid markets where pricing is slower to update.

How to Use the Sure Bet Calculator

Select the number of outcomes — 2 (tennis, basketball), 3 (football 1X2), or more
Enter the best available odds for each outcome from different bookmakers
Enter your total stake budget in pounds
Read: whether an arb exists, the optimal stake for each outcome, and your guaranteed profit

The Maths: Identifying an Arbitrage

The arbitrage condition: the sum of the inverse of each outcome's odds (the implied probabilities) must be less than 1.

Two-outcome example (tennis):

Bookmaker A prices Player 1 at 2.10. Bookmaker B prices Player 2 at 2.05.

Sum of inverses = 1/2.10 + 1/2.05 = 0.476 + 0.488 = 0.964

Since 0.964 < 1, an arb exists. The arb margin is (1 - 0.964) = 3.6% — your guaranteed return on total stakes.

Optimal stake calculation for £1,000 total budget:

Stake on Player 1 = £1,000 x (1/2.10) / 0.964 = £494 Stake on Player 2 = £1,000 x (1/2.05) / 0.964 = £506

Total staked: £1,000. Whatever happens: £494 x 2.10 = £1,037, or £506 x 2.05 = £1,037. Guaranteed profit: £37 (3.7%).

Three-outcome example (football 1X2):

Bookmaker A: Home win 2.40. Bookmaker B: Draw 3.80. Bookmaker C: Away win 3.20.

Sum of inverses = 1/2.40 + 1/3.80 + 1/3.20 = 0.417 + 0.263 + 0.313 = 0.993

Since 0.993 < 1, an arb exists with a 0.7% margin. On a £1,000 budget:

Stake on Home = £1,000 x 0.417 / 0.993 = £420 Stake on Draw = £1,000 x 0.263 / 0.993 = £265 Stake on Away = £1,000 x 0.313 / 0.993 = £315

Whichever outcome occurs, return ≈ £1,007. Profit: £7 guaranteed.

Tips and Strategies

Act immediately. Arb windows typically last minutes or less before prices are corrected. Have your accounts funded and ready to place without delay.
Use multiple bookmaker accounts. Maintaining accounts at 10 or more bookmakers maximises the frequency of arb opportunities you can access.
Factor in withdrawal times and float. Funds spread across multiple bookmakers need replenishment. Each bookmaker requires a working balance — manage your total float across accounts carefully.
Start with larger markets. Football, tennis, and basketball main markets have the most frequently arbed pricing and the most liquid odds feeds.
Accept that account restrictions will come. Bookmakers routinely limit accounts of bettors who consistently take the best prices. Mixing in some recreational single bets can extend account longevity, though eventually restrictions are almost inevitable for prolific arbers.

Frequently Asked Questions

Is arbitrage betting legal? Yes, arbitrage betting is completely legal in the UK. You are exploiting price differences between bookmakers — there is no rule against it. However, bookmakers are private companies and are entitled to limit or close accounts at their discretion.

Why do arbitrage opportunities exist? Bookmakers set prices independently and cannot always monitor every competitor in real-time. Price discrepancies emerge most often around breaking team news, at market opening, and in less liquid markets where pricing models respond slowly.

Can I lose money from a sure bet? If stakes are calculated correctly and all bets are placed and accepted, you cannot lose from a pure arb. Risks include: one bookmaker voiding your bet after the event, a bet not being accepted at the intended odds (price changed), or a staking error. Always double-check all bets before placing.

How much can I make from arbitrage? Individual arb margins are typically 0.5–5%. Volume determines total profit. Serious arbitrage bettors place dozens of arbs per week across many bookmakers, turning small percentage margins into meaningful monthly income through volume.

Will bookmakers close my account for arbing? Yes, most bookmakers will eventually limit the maximum stake they accept from bettors they identify as consistent arbitrage players. Maintaining a low profile — not always taking the maximum, occasionally placing recreational bets — can extend account longevity, but restrictions are a known occupational risk for arbers.