Arbitrage in one line
An arbitrage exists when the best available price for every outcome, taken across different bookmakers, has implied probabilities that add up to less than 100%. Split a stake across those prices in the right proportions and every outcome pays back more than was staked.
A worked example
Bookmaker A offers 2.10 on Team X, bookmaker B offers 2.15 on Team Y, a straight two-way market. Implied probabilities: 1 ÷ 2.10 = 47.6%, 1 ÷ 2.15 = 46.5%, adding up to 94.1%, under 100%. Staking roughly 50.6 on X and 49.4 on Y (100 total) returns about 106.2 whichever side wins: a locked-in 6.2% profit. That is a large one, picked to make the sums easy; real gaps between licensed bookmakers are usually 1 to 3%.
Why it's harder than it looks
The prices have to be live at both bookmakers at the same moment you place both bets; odds move, and a price can vanish between the first bet and the second. It also needs a funded account at every bookmaker involved, in the same currency ideally, and the stake has to be split precisely for the numbers to work.
Bookmakers actively look for arbing patterns, since an account that always bets both sides of a market is a clear tell, and they tend to limit or close those accounts faster than accounts that just win.
When a sure bet looks too good
Lists of sure bets sometimes show 15, 20 or even 50% profit. Those are data errors, not opportunities: a price that hasn't been updated, a market read wrongly (a handicap compared with a match result, say), or a price the bookmaker will void as an obvious error under its terms.
If one leg is voided after the other is placed, you're left with an ordinary single bet with no cover, often at a poor price. The bigger the advertised profit, the likelier that is.
Arbitrage vs. +EV betting
Arbitrage is close to risk-free on a single event, but the margins are usually small and fragile, and the account-limiting problem is worse than for +EV betting.
+EV betting takes on real variance on every individual bet, but a real edge doesn't depend on catching a rare price gap, and it's the approach Sharp Bets is built around: find prices better than the fair odds, size the stake to the edge, and let the sample size do the work over hundreds of bets rather than one.
Common questions
Is arbitrage betting legal in Sweden?
Yes. Placing bets at licensed bookmakers is legal whatever your reason. But their terms let them limit accounts, and accounts that arb get limited quickly.
How big is a normal sure bet?
Usually 1 to 3%, often less. A sure bet showing 15% or more is almost always a stale or wrong price.
Is a sure bet risk-free?
No. A price can move between your two bets, a bookmaker can void a bet placed at an obvious error, and your stake can be limited. Each of these leaves you with an uncovered bet.
Does Sharp Bets show sure bets?
No. It shows +EV picks: prices above Pinnacle's fair odds at eleven Swedish-licensed bookmakers.