Enter the best available price on each outcome — from any combination of bookmakers — and see whether the total implied probability is under 100%. If it is, that's a sure bet: we calculate the exact stake split so every outcome pays you the same guaranteed return.
| Outcome | Stake | Return if this wins |
|---|---|---|
| 1 | €49.40 | €103.73 |
| 2 | €50.60 | €103.73 |
Arbitrage betting — often shortened to arbing, or called a sure bet / arb — means backing every possible outcome of the same event at different bookmakers, at prices good enough that you profit no matter what happens. It doesn't rely on predicting the result at all; it's pure price-matching.
It works because bookmakers don't all price a market identically. Every single book's own price already implies more than 100% (that's their vig — see our no-vig calculator below). But when you shop across books and take each outcome's single best price, those best prices can occasionally combine to a total implied probability under 100%. That gap between 100% and the combined price is your risk-free margin, before staking costs or limits.
The stakes aren't equal in euros — they're proportional to each price's implied probability, so that whichever outcome actually happens, your payout from that leg is identical. A bigger stake goes on the shorter (more likely) price, a smaller stake on the longer one; the calculator above works this split out for you automatically.
It's a set of bets on every possible outcome of the same event, placed at different bookmakers, where the combined odds guarantee a profit regardless of the result. It happens when the single best price for each outcome — taken across multiple books — sums to a total implied probability under 100%.
Proportionally to each outcome's implied probability (1 ÷ decimal odds), so that every outcome returns the same amount: stake on outcome i = total stake × (1 ÷ odds_i) ÷ (sum of 1 ÷ odds across all outcomes). The calculator above does this automatically — that's exactly the 'stake to place' column.
It's legal — you're just placing normal bets. But it isn't against any rules for a bookmaker to limit or close an account it identifies as an arber, and most soft books actively look for the pattern (backing every side of a market for a small, consistent margin). Sure betting tends to be a short-lived strategy at any one book rather than a sustainable long-term edge.
Odds move constantly as books balance their liability and react to each other's lines, so a gap under 100% often closes within seconds to minutes — sometimes before you finish placing the second leg. True arbs are also thin (often under 2-3% margin), so bet-size limits and rounding can eat the edge entirely even when you do get both bets down.