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Arbitrage calculator

Enter the best price you can find for each outcome. The calculator splits your stake so every result pays the same, and tells you whether the prices actually make a sure bet.

Outcomes
Prices

Commission is for exchanges (Betfair, Smarkets, Matchbook). Leave it at 0 for bookmakers.

Outcome 1
Outcome 2

Split across every outcome.

Round stakes

Exact stakes, to the cent.

Result

Sure bet
    Total staked
    –
    Returns
    –
    Min. profit
    –

    How the stake split works

    For a sure bet, you want the same payout whichever outcome wins. So each outcome gets a share of the total stake in proportion to 1 divided by its odds:

    stake on outcome i = total × (1 / odds i) ÷ Σ (1 / odds) margin = 1 ÷ Σ (1 / odds) − 1

    If Σ (1 / odds) is below 1, the shared payout is bigger than the total stake and you have an arb. If it's 1 or more, every split loses money, which is the normal state of affairs: that excess is the bookmakers' margin.

    A worked example

    One bookmaker offers 2.12 on Over 2.5 goals and another offers 2.02 on Under 2.5. With €1,000 in total, 1 / 2.12 = 0.4717 and 1 / 2.02 = 0.4950, which add up to 0.9667. The stakes come out at €487.92 and €512.08. Either bet pays back about €1,034.40, a profit of €34.39, or 3.44%, whatever the score. That example is loaded when you open this page.

    Commission, rounding and fixed stakes

    Commission. Exchanges take a cut of net winnings, so a price of 2.02 at 2% commission really pays 1.9996. The calculator sizes each leg on what it actually pays.

    Rounding. Light, natural and heavy rounding move stakes onto the round numbers ordinary punters use, with steps that grow with the stake. Rounding makes the payouts slightly unequal, so the guaranteed profit is the smallest of them. If a rounding mode would cost more than a third of the margin, the calculator drops to a finer one and tells you. The ArbVantage dashboard uses the same logic.

    Fixed stake. If a bookmaker only lets you bet €150, or you've already placed one leg, press “Fix this stake” on that leg and enter the amount. The other stakes are worked out around it.

    What can still go wrong

    A sure bet is only sure once every leg is placed at the price you calculated. Odds move, stakes get capped, and bookmakers can void bets placed at obvious pricing mistakes. Check each price at the bookmaker before you bet, and place the leg that is most likely to move first. Margins are usually small (1–3%), so a single failed leg can wipe out the profit from many good ones.

    FAQ

    Arbitrage calculator questions

    What is an arbitrage bet?
    A set of bets that covers every outcome of an event, each at a different bookmaker, priced so that every outcome pays back more than the total you staked. It works because bookmakers set their prices independently and sometimes disagree by enough that the combined implied probability drops below 100%. People also call it a sure bet or an arb.
    How do I know if two prices are an arb?
    Add up 1 divided by each decimal price. If the total is under 1 (under 100%), it's an arb, and 1 divided by that total, minus 1, is the margin. 2.12 and 2.02 give 0.4717 + 0.4950 = 0.9667, so the margin is 1 / 0.9667 − 1 = 3.44%. The calculator does this for you and shows the implied total at the top of the result.
    Should I round my stakes?
    Most people who bet arbs regularly do. Stakes like €487.92 are a classic sign of arbitrage to a bookmaker's trading team, while €490 looks like an ordinary bet. Rounding costs a little margin, because the payouts are no longer exactly equal. The calculator falls back to finer rounding if your chosen mode would cost more than a third of the edge.
    How does exchange commission change the stakes?
    Exchanges such as Betfair, Smarkets and Matchbook take a percentage of your net winnings. A 2.02 back bet at 2% commission really pays 1 + 1.02 × 0.98 = 1.9996. Enter the commission on that leg and the calculator sizes every stake on what each bet actually pays, so the profit shown is after commission.
    What if the odds change after I place the first leg?
    Put the new price into the calculator, fix the stake you've already placed with “Fix this stake”, and it works out the new stake for the remaining leg. You'll often still lock in a smaller profit, or a small loss that is better than leaving the first bet uncovered. Placing the leg at the bookmaker most likely to move or cap you first reduces this risk.
    Is the calculator free? Do you see what I type?
    It's free and needs no account. All the maths runs in your browser and nothing you type is sent to us. Your inputs are kept in the page address, so you can bookmark a calculation or send it to someone with “Copy link”.

    More free tools

    Find these automatically

    Spotting arbs by hand means comparing dozens of bookmakers before the prices move. ArbVantage scans 25+ bookmakers, re-checks the odds every few minutes and opens each sure bet with the stakes already split, rounded the way you like. Free for 7 days.

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