For bettors

Arbitrage calculator

Put the best odds for each outcome from different books. If the total implied probability is under 100%, there is a locked-in profit — this splits the stakes for you.

Odds

Outcome 1

Outcome 2

Total stake

Result

Arb margin

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Guaranteed profit

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Guaranteed return—

ROI—

Real arbs are rare, small and short-lived: odds move while you place the second leg, limits get cut, and books void bets they judge to be arbing. Treat this as the maths, not a strategy.

How arbitrage betting works

An arbitrage — an "arb" or "sure bet" — exists when the best available prices for the different outcomes of an event, taken from different bookmakers, together imply a probability of less than 100%. Convert each price to its implied probability with 1 ÷ decimal odds and add them up. If the sum is 0.98, you can back every outcome and be guaranteed to get back about 1 ÷ 0.98 ≈ 1.02 times your total stake no matter which result lands — a 2% locked profit.

Splitting the stakes

The calculator sizes each bet so the return is identical whichever outcome wins. Each outcome receives total stake × (1 ÷ its odds) ÷ (sum of 1 ÷ odds). Round to the nearest bettable amount and the profit shifts by a few cents between outcomes — the tool shows the worst case.

Why the edge rarely survives contact

Arbs are small and short-lived, and bookmakers treat consistent arbitrage as a reason to limit or close an account. By the time you place the second leg the price has often moved, the stake you wanted may exceed the book's limit on that market, and a bet flagged as an arb can be voided after the fact. Treat the calculator as a check on whether an opportunity is real, not a guarantee you can take it.

Frequently asked questions

How do I know if an arbitrage exists?

Add 1 ÷ odds for every outcome. If the total is under 100%, backing all outcomes locks in a profit. Over 100% and every split guarantees a loss.

How are the stakes split in an arbitrage?

Each outcome gets total stake × (1 ÷ its odds) ÷ (sum of 1 ÷ odds), so every outcome returns the same amount regardless of the result.

Why are real arbitrage bets hard?

They are small, brief and closely watched. Odds move while you place the second leg, books cut limits, and many void bets they judge to be arbing.

What counts as a good arbitrage percentage?

Most real arbs are between 0.5% and 2.5%. Anything above 4–5% almost always means a price is about to be corrected, a bet will be voided, or you have misread the market (for example a different handicap line).

Do the two bets need equal stakes?

No. Stakes are inversely proportional to the odds — the shorter-priced outcome gets more money. Equal stakes only balance when the odds are equal, which is not an arbitrage.

Does the calculator handle three-way markets and draws?

Yes. Add a row per outcome — 1X2 football, three-way moneylines, any number of mutually exclusive results. The same rule applies: the implied probabilities must sum to under 100%.

What about currency and exchange commission?

If the two books settle in different currencies, an FX move between placing and cashing out can erase a thin arb. On a betting exchange, the commission on winnings (typically 2–5%) comes straight off the margin — subtract it before deciding the arb is worth it.

Is arbitrage betting legal?

Placing bets at favourable odds is legal wherever betting itself is legal. It is not against the law, but it is against most bookmakers' terms of service, which is why arbitrage accounts get restricted. This tool does the maths and takes no position on whether you should do it.

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