What is arbitrage betting?
Arbitrage betting, also called a surebet or an arb, means backing every outcome of one market with different bookmakers, so you win more than you stake whatever happens.
It works because bookmakers don't always agree. Each one builds a margin into its own odds, so on one site the outcomes add up to more than 100%. But when you take the best odds for each outcome from different bookmakers, they can add up to less. That gap is your profit.
Why arbs exist
Every bookmaker sets its own odds. Some build them with their own traders and models, others buy them from a supplier and adjust them. They also have different customers to manage: a bookmaker full of fans of one club will shorten that club's odds to limit its risk, while another doesn't need to.
So two bookmakers can look at the same match and land on different odds. Most of the time the gap is small and their margins cover it. When one is far enough out of line, the best odds across the market add up to less than 100%, and that is an arb.
When arbs appear
Arbs are most common when a market first opens. The first odds are a bookmaker's own estimate, before many bets have been placed. As bettors put money on the outcome they think is too generous, the bookmaker shortens it, and the odds across bookmakers move closer together.
They also open up when news breaks, like a team line-up or an injury, because some bookmakers update faster than others. And they are more common in player props and smaller leagues, where bookmakers take less money and move more slowly than on the match result in the big leagues. Either way an arb rarely lasts long, so speed matters.
How to use the arbitrage calculator
- 1
Pick 2 or 3 outcomes. 2 for over/under, both teams to score or a player prop. 3 for the match result.
- 2
Enter the best odds for each outcome. Decimal, fractional and American odds all work.
- 3
Set your total stake. Already placed one bet? Lock its stake and the others are sized around it.
- 4
Place every bet quickly. Odds move, so place the stakes shown before they change.
How to calculate an arb
Turn each outcome's odds into an implied probability with 1 ÷ odds, and add them up. If the total is under 100%, you have an arb.
Market total = 1 ÷ odds 1 + 1 ÷ odds 2
Stake per outcome = total stake × (1 ÷ odds) ÷ market total
With odds of 2.10 and 2.05 the market total is 96.40%. On a 100 stake you put 49.40 on one side and 50.60 on the other, and either way you get back 103.73.
On a 2-way market, 2.00 against 2.00 breaks exactly even, and so do 1.50 against 3.00 and 1.25 against 5.00. Anything higher on either side is an arb.
Examples
Load any example into the calculator to change the odds or the stake.
Over/under 2.5 goals
One bookmaker offers 2.10 on over 2.5 goals, another 2.05 on under. Together the odds add up to under 100%.
| Outcome | Odds | Stake | Return |
|---|---|---|---|
| Over 2.5 | 2.10 | 49.40 | 103.73 |
| Under 2.5 | 2.05 | 50.60 | 103.73 |
Profit 3.73 on 100.00, a return of 3.73%.
Match result
Three bookmakers, each with the best odds on one outcome. 3-way arbs are rarer and smaller, but they happen around team news.
| Outcome | Odds | Stake | Return |
|---|---|---|---|
| Home | 2.30 | 87.46 | 201.16 |
| Draw | 3.60 | 55.88 | 201.16 |
| Away | 3.55 | 56.66 | 201.16 |
Profit 1.16 on 200.00, a return of 0.58%.
Bookmaker against an exchange
Over 1.5 shots at a bookmaker, under 1.5 on an exchange that takes 2% commission on winnings. The commission brings 2.00 down to 1.98.
| Outcome | Odds | Stake | Return |
|---|---|---|---|
| Over 1.5 shots | 2.10 | 48.53 | 101.91 |
| Under 1.5 shots | 2.00 | 51.47 | 101.91 |
Profit 1.91 on 100.00, a return of 1.91%.
Where to find arbs
Arbs come from comparing odds: the more bookmakers you check, the more often one is out of line. They turn up most in player props and smaller leagues, where bookmakers are slower to move than on the match result in the big leagues.
Odds Outliers shows the odds that stand out from the average of every bookmaker we track, which is where most arbs start.
Football rules that break an arb
An arb only works if every bet settles the same way. In football these catch people out:
- A player who doesn't start. One bookmaker voids a player prop when the player comes off the bench, another settles it as a loss. Void rules
- 90 minutes or extra time. Most markets settle on 90 minutes plus stoppage time, but some cup markets include extra time.
- Asian lines. Over 2.5 and under 2.5 can't both lose. Over 2.25 against under 2.5 can lose half, so it isn't an arb.
- Odds that look too good. Odds far above the market can be voided as a mistake after you placed the other bet. Palpable error
- Different stat sources. Shots, tackles and saves can come from different data providers, so one bet wins and the other loses on the same match.
Risks and limits
An arb is only guaranteed once every bet is placed at the odds you calculated. Odds can move between your first and last bet, and a bookmaker can accept only part of your stake.
Most arbs return 1 to 3%, so one bet that is voided or settled differently can wipe out the profit of many others. And bookmakers can limit accounts that keep taking odds above the market. Why bookmakers limit accounts
Is arbitrage betting legal?
Yes. Betting with several bookmakers is legal wherever betting is legal, and arbing breaks no law. It can break a bookmaker's terms, which is why accounts get limited. Rules on betting and tax differ by country, so check your own.