What is Arbitrage Betting?

The short answer

Arbitrage betting (also called "arbing" or "sure bets") exploits the fact that different bookmakers set different odds for the same event. By covering all possible outcomes across multiple bookmakers, you can mathematically guarantee a profit regardless of the final result — as long as the combined implied probability of all outcomes is below 100%.

How arbs work — a simple example

Imagine a tennis match between Player A and Player B. Two bookmakers price it differently:

• Bookmaker 1: Player A wins at 2.10
• Bookmaker 2: Player B wins at 2.10

Implied probability of each: 1 ÷ 2.10 = 47.6%. Combined: 47.6% + 47.6% = 95.2% — below 100%. An arb exists.

With a total stake of £100 (£50 on each), your guaranteed return is £50 × 2.10 = £105 whichever player wins — a locked-in profit of £5 (5%).

The arb percentage formula: (1/odds_A + 1/odds_B) × 100. Any result below 100 is a valid arb. The further below 100, the larger the profit.

Types of arbitrage

Bookmaker-to-bookmaker arb

The classic form. Two traditional bookmakers price the same market differently, usually due to different models, early prices, or deliberate lines to attract action. Margins are typically small (1–3%).

Back-lay arb (exchange arb)

Back an outcome at a bookmaker, then lay it on the Betfair Exchange at lower-than-back odds. This is the most reliable arb type because exchange lay odds are driven by liquidity rather than individual bookmaker pricing. Margins are often larger and the arb doesn't close as quickly.

Reload bonus / promotion arb

Bookmaker promotions (enhanced odds, free bets, cashback offers) temporarily make certain bets higher value. Combining these with a lay on the Exchange converts a "bonus bet" into guaranteed cash — this is the principle behind "matched betting", which is technically arb with a softer edge.

Finding arbs

Manual scanning is almost impossible at volume — odds move within seconds. Most professional arbers use dedicated arb alert services that scan hundreds of bookmakers simultaneously and notify when a valid combination appears. Free and paid services exist; paid ones tend to have faster alerts (sub-second) and better filters.

For back-lay arbs, Arbworld's Dropping Odds tables and Moneyway tables are useful starting points — sharp price moves on the Exchange often precede matching opportunities at bookmakers that are slower to update.

The real risks

• Account restrictions. Bookmakers actively monitor for arb behaviour and will limit or close winning accounts — often within weeks of first arb activity. Once limited, the maximum stake is reduced to near-zero, killing the opportunity.
• Odds changes. If one leg of your arb changes between placing both bets, you may end up with a losing position rather than a locked profit. Always confirm both legs are available before placing either.
• Stake rounding. Exact stake calculations often require fractions of a penny. Rounding to the nearest unit introduces a small one-sided exposure.
• Withdrawal friction. Balances spread across many bookmakers create operational overhead. Some bookmakers restrict withdrawals or require turnover before they pay out.
• Terms & conditions. Many bookmakers void bets placed as part of obvious arb activity, citing vague "abuse" clauses in their T&Cs.

Arbitrage vs value betting

Arbing locks in a small guaranteed profit. Value betting involves placing bets where you believe the odds exceed the true probability — no guarantee, higher variance, but potentially far better returns long-term if your edge is real. Professional bettors typically use both approaches at different stages. Arbing is considered lower-skill; value betting requires a working probability model.

Try the Arbworld Arb Calculator

Use our free Arb Calculator to calculate exact stakes for two-way and three-way arbs, see the guaranteed profit, and check whether a combination is actually profitable after rounding.