This free arbitrage calculator (or arbing calculator) checks whether two odds on a two-way market add up to less than 100% and, if they do, shows exactly how much to stake on each side for an equal return.
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The bar shows the combined implied probability; the line marks 100%. Under 100% is an arbitrage. Odds and limits can change before both bets are placed.
How to use the arbitrage calculator
The arbitrage calculator above is built for two-way markets, where only two outcomes are possible. It updates as you type.
- Enter the best decimal odds you can find for outcome 1 and for outcome 2. They will usually come from two different bookmakers.
- Enter the total amount you want to put into the arb.
- Read the total implied percentage. If it is under 100%, the calculator shows an arbitrage and splits your stake so that both outcomes return the same amount.
- Tick “round stakes” if you prefer whole amounts. Rounding moves the returns slightly apart, and the profit shown is always the worst case.
If your prices are in fractional or American format, convert them first with our odds calculator.
How a two-way arbitrage works
Each price implies a probability: 1 ÷ decimal odds. In a normal market the two probabilities add up to more than 100%, and the difference is the bookmaker margin. Sometimes two bookmakers disagree enough that the best prices add up to less than 100%. That gap is the arbitrage.
Example: outcome 1 is priced at 2.10 and outcome 2 at 2.05. The implied probabilities are 47.62% and 48.78%, a total of 96.40%. With a total stake of 100, the arbitrage calculator puts 49.40 on outcome 1 and 50.60 on outcome 2. Whichever side wins, the return is about 103.73, a profit of 3.73 or 3.73% of the stake.
The same example in the arbitrage calculator: 96.40% in total, so both outcomes return 103.73.
The formula behind the stakes is: stake on an outcome = total stake × (1 ÷ its odds) ÷ total implied probability. The return on the whole arb is 1 ÷ total implied probability − 1.
Which football markets suit two-way arbitrage
Any market with exactly two outcomes and no third result works. In football the most common are:
- Over/Under goals lines such as 2.5, where a draw on the line is impossible. See our over/under 2.5 goals guide.
- Both Teams to Score: Yes or No.
- Asian handicap lines with a half goal, for example -0.5 and +0.5, explained in our Asian handicap guide.
- Draw No Bet, where a draw returns the stake on both sides.
Three-way markets such as the 1X2 need three stakes, so this two-way arbing calculator is not the right tool for them.
Arbing calculator or arbitrage software?
“Arbing” is simply the bettors’ word for arbitrage betting, so an arbing calculator, an arb calculator and an arbitrage calculator are the same thing. Paid arbitrage software scans hundreds of bookmakers to find the prices. A calculator does the second half of the job: once you have two prices, it checks whether they form an arb and tells you exactly how much to stake on each side.
The risks of arbitrage betting
An arb is only risk-free if both bets are accepted at the prices you saw. In practice several things can go wrong:
- Odds move. A price can drop in the seconds between your two bets, which can turn a profit into a loss.
- Stake limits. A bookmaker may accept only part of your stake on one side.
- Account restrictions. Many bookmakers’ terms allow them to limit or close accounts that bet this way.
- Voided bets. A price posted by mistake can be cancelled under the bookmaker’s rules, leaving the other bet uncovered.
- Different rules. Bookmakers can settle the same market differently, for example after extra time or an abandoned match.
Check both prices and both betting slips before you confirm, and start with small amounts while you learn.
Frequently asked questions
Is arbitrage betting legal?
In most countries placing bets with licensed bookmakers is legal, and arbitrage is just a way of choosing prices. It is, however, often against bookmakers’ terms, which is why accounts get limited. This is general information, not legal advice.
What is a good arbitrage percentage?
Most genuine two-way arbs return between about 1% and 5%. Much higher numbers usually mean a mistake in the odds, a different market or a price about to be cancelled.
Why does the calculator say there is no arbitrage?
Because the total implied percentage is 100% or more. That is normal: almost every market carries a bookmaker margin, and only occasional price differences create an arb. You can learn how margins work in our guide to football odds.
18+. Betting involves risk and you should never stake more than you can afford to lose. This arbitrage calculator is for information only. If gambling stops being fun, support is available at BeGambleAware.org.