Arbitrage calculator, also known as a surebet calculator. One bookie has a tennis match at 2.20, another has the other player at 2.05. Back both sides with the right split and you win whoever wins. That’s the whole idea.
With C$100 total, put C$48.24 on the 2.20 and C$51.76 on the 2.05. Either way you get back about C$106.12. Six dollars and twelve cents, no matter what happens on court.
What the arbitrage calculator checks
Every price hides a probability. 2.20 means the bookie thinks about 45.5%. 2.05 means 48.8%. Add them up and you get 94.2%. Below 100% means the two bookies together are underpricing the match, and that gap is your profit.
Market total = 1/odds₁ + 1/odds₂ (+ 1/odds₃) Stake on one side = total stake × (1/odds) ÷ market total Profit = total stake ÷ market total − total stake
Three-way markets like home, draw and away work the same. Add a third line.
Before you place anything
Real surebets are small and they don’t last. One to three percent is normal. Anything bigger usually means a typo on the bookie’s side or a market that’s already been suspended, and those bets can get voided.
A few habits that save money:
- Place the bet on the side most likely to move first. If the second price is gone by the time you get there, you’re left holding a normal bet.
- Check the rules match. One bookie settling a retirement as a loss and the other voiding it can turn a surebet into a loss.
- Expect limits. Bookmakers don’t like arbers, and an account that only bets arbs tends to get restricted fast.
You need accounts at several bookies to arb at all, and money sitting in each of them. The more books you can compare, the more arbs you’ll find.
It’s legal almost everywhere. It’s just not something bookies want you doing.
Three-way markets
Football is where most arbs show up, because three outcomes means three chances for one bookie to be out of line. Say you find home at 2.30, the draw at 3.60 and away at 4.20, all at different bookies. That’s 43.5% + 27.8% + 23.8% = 95.1%. Under 100, so it’s an arb.
On a C$100 total, the calculator splits it C$45.74 on the home win, C$29.22 on the draw and C$25.05 on the away win. Whatever happens, you get back C$105.19. A 5.2% arb is rare, and when you see one that big, check the prices are still live before you place anything.
Exchanges and commission
If one side of the arb is on a betting exchange, the exchange takes commission from your winnings there. A 2.20 on an exchange with 2% commission is really worth about 2.18. Knock the price down before you put it in, or a 1% arb can turn into a 0.5% one, or nothing.