Betting with several bookmakers is not usually prohibited, but each has its own terms and may limit your account. Read the terms of the bookmaker you use and the regulations in your country.

Are they really risk-free?

Not entirely. The maths has no risk if every bet is accepted at those odds and all bookmakers settle the same way, but in practice that can fail.

What does it mean when the calculator says there is no surebet?

That the sum of probabilities is 100% or more. At those prices, covering all outcomes would lose you money or leave you even.

Can I calculate more than 3 outcomes?

This calculator covers 2 and 3 outcomes, the usual cases. The formula is the same for more: just add one term per outcome.

Surebet calculator: split your stake on 2 and 3 outcomes

Enter the odds and the total stake. The calculator tells you whether there is a surebet and how to split the amount so every outcome pays the same.

What a surebet is

A surebet, or arbitrage, appears when the odds from several bookmakers on all the outcomes of a market are so high that, by splitting the money correctly, you collect the same whatever happens and more than you staked. It happens because each bookmaker sets its prices separately, and for a while they may disagree.

In theory it does not depend on the result. In practice, there are risks that the word sure hides, explained further down.

The formula

Sum = 1 ÷ odds₁ + 1 ÷ odds₂ (+ 1 ÷ odds₃)

If the sum is below 1, there is a surebet.

Stake on each outcome = total stake × (1 ÷ odds) ÷ sum

Guaranteed payout = total stake ÷ sum

Example with 2 outcomes

Odds of 2.10 and 2.05 at two different bookmakers, with €100 in total.

Sum: 0.4762 + 0.4878 = 0.9640, below 1
Stake on the first: €49.40
Stake on the second: €50.60
Payout either way: €103.73
Profit: €3.73

Example with 3 outcomes

A 1X2 market at 2.20 / 3.60 / 3.90, with €100 in total.

Sum: 0.4545 + 0.2778 + 0.2564 = 0.9887
Stakes: €45.97, €28.09 and €25.93
Payout: €101.14
Profit: €1.14

Risks the formula does not show

Price changes. Surebets are short-lived. If a price drops between your first and second bet, you can be left with a position that loses money.
Rejected or limited bets. The bookmaker may accept only part of the stake, and then the split no longer works.
Each bookmaker’s rules. How they treat a tennis retirement or extra time does not always match. If an outcome is voided at one bookmaker and not at the other, you can lose.
Pricing errors. An unusually high price may be a mistake, and the bookmaker’s terms may let it void that bet. It is a common cause of a false surebet.
Account limits. Many bookmakers restrict accounts that place this type of bet. Check their terms.

Common mistakes

Checking only one price. You must cover every possible outcome of the market.
Forgetting commission. On an exchange, commission reduces what you actually collect, so subtract it before calculating.
Rounding stakes carelessly. With margins of 1%, heavy rounding can eat the profit.

The sum in the formula is the same one used for the bookmaker margin: check it with the implied probability calculator. And if you place this kind of bet, record each leg: only your real yield, measured across your whole history, will say whether the numbers add up. The import guides explain how to do it.

Surebet calculator for 2 and 3 outcomes