Sure betting explained: how arbitrage betting works

What a sure bet is

A sure bet, also called an arb or arbitrage bet, is a set of bets on every outcome of one event, placed at different bookmakers, where the odds are high enough that every outcome pays back more than you staked in total. You are not predicting anything. You use the fact that two bookmakers disagree on the price.

The name oversells it. The result only works out if every leg is placed at the shown odds and stands. The margin per sure bet is small, usually 1% to 2% of the total stake, and most of this guide is about the gap between "the maths works" and "the money arrives".

Why odds disagree between bookmakers

Every bookmaker sets and moves its own prices. They use different models, react to team news at different speeds and manage their own liabilities. A bookmaker with many recreational customers in Austria might shade the price on Red Bull Salzburg because that is where its customers' money goes, while another moves its line within seconds of informed money arriving.

For a few minutes, sometimes longer, one bookmaker can be out of step with the rest of the market. If Bookmaker A is generous on one outcome and Bookmaker B is generous on the other, the two best prices together can add up to less than 100% implied probability. That gap is the sure bet.

The 1/odds test and the margin

Decimal odds, the format used across Austria and Germany, convert to implied probability with one division:

implied probability = 1 / decimal odds

Add the implied probabilities of the best price for each outcome. A normal market adds up to more than 1, because the bookmaker's margin is built in. If the sum is below 1, you have a sure bet.

S = 1/oddsA + 1/oddsB (+ 1/oddsC)
S < 1 → sure bet

There are two common ways to quote the size of the edge: profit as a share of the total stake, or return on the money staked. ArbVantage shows the second.

profit % of total stake = (1 − S) × 100
return on stake % = (1/S − 1) × 100

The difference is small for typical sure bets, but worth knowing when you compare numbers from different sources.

Splitting your stakes on a 2-way market

The goal is the same payout whichever side wins. You get that by staking each leg in proportion to its implied probability:

stake A = total × (1/oddsA) / S
stake B = total × (1/oddsB) / S
payout = total / S

Rounded stakes are easier to type and check, for example €495 and €505. The payouts become €1,039.50 if Player 1 wins and €1,035.25 if Player 2 wins. Both are still above €1,000, just uneven. ArbVantage shows what rounding does to each outcome before you place anything.

A 3.6% margin is on the high side. Most pre-match sure bets you will see are between 1% and 2%.

A 3-way example: football 1X2

Football match-result markets have three outcomes: home, draw, away. The method is identical with a third term.

S = 1/oddsH + 1/oddsD + 1/oddsA
stake X = total × (1/oddsX) / S

Three legs means three chances for something to go wrong, and €5.58 is not much of a cushion. That is typical: the margins are thin, so execution matters more than anything else.

What a sure bet earns

The profit on one sure bet is simple:

profit = total stake × margin

€600 across two bookmakers at a 1.5% margin returns about €9, if both legs stand. Three things decide what that adds up to over a month:

• Turnover. Your stake is tied up from the moment you bet until the match is settled, usually one to three days before kick-off. In our example the same euro is staked about 13 times a month (26 active days, three quarters of the money usable, about 1.5 days tied up per bet).
• Spread across accounts. Money sits in separate bookmaker accounts, and a leg can only go where you have balance. In practice about three quarters of your bankroll is usable at any moment, and one sure bet uses at most about a sixth of it. The bankroll guide covers how to split it.
• Limits. Bookmakers cap the stake on a single bet and lower it once they see you win steadily.

For scale: with our model (a realised margin of 1.5%, stakes of at most €1,000, money reused about 13 times a month), €1,000 of profit in a month would take about €67,000 in stakes, roughly 67 sure bets of €1,000, more than most accounts accept for long. Most people never get there, because bookmakers limit winning accounts, and the €97 subscription comes off the top. With €1,000 in your accounts and an hour a day, the same model gives −€47 to +€123 a month after the subscription, from the month once bookmakers limit you to a typical month before limits. Try your own numbers in the earnings calculator; its results can be negative too.

The real risks

On paper a sure bet removes the risk of the result. These are the things that put risk back.

• The price moves before your second leg. This is the most common problem. You get on at 2.10, then the other bookmaker drops from 2.05 to 1.90. Now you either accept a small loss or leave one side open. Place the leg most likely to move first, usually the outlying price.
• Obvious errors and voids. If one price was a clear mistake, the bookmaker may void that bet under its terms. You are then left with an unhedged bet at the other bookmaker. A sure bet showing 8% or more deserves suspicion, not excitement.
• Different settlement rules. Bookmakers disagree on tennis retirements (some settle after one set, some void), on whether a market includes extra time, and on dead heats. Two legs settled under different rules can both lose.
• Betting tax in Germany. Germany charges 5.3% on sports bets, and some bookmakers pass it on by cutting your stake or your winnings. Leave it out of the maths and a 2% margin turns into a loss. The tax and legality guide explains the rules in Austria and Germany.
• Stake limits. A bookmaker may accept only part of your stake, which unbalances the bet. Accounts that win steadily get restricted over time. See how bookmaker limits work.
• Rounding and minimums. Rounding, minimum stakes and currency conversion all shave the margin. On a 1% sure bet, a few euros of rounding can wipe it out.
• Licensing. Not every bookmaker is licensed in Austria or Germany. ArbVantage never hides them; it shows a neutral flag for the country you bet from, such as "Not licensed in Germany (GGL whitelist)" or "Not licensed in Austria", so you can decide where you bet. Our tax and legality guide explains the flags.

Placing a sure bet: a practical checklist

1. Check it is the same event, the same market and the same line, for example both legs "90 minutes plus stoppage time".
2. Check the settlement rules at both bookmakers for this sport, especially retirements and voids.
3. Confirm both prices are still live and the margin is above your minimum, say 1%, after any betting tax.
4. Work out the stakes and decide on rounding before you start.
5. Place the most fragile leg first, usually the outlying price.
6. Confirm it was accepted in full at the expected odds, then place the other leg straight away.
7. Record both bets so you can reconcile results and spot rule differences later.

Only stake money you can afford to lose. Mistakes happen to everyone, and one bad void can cost more than ten good sure bets earn.

Information, not betting advice. 18+. Betting involves risk. If betting stops being fun, see our responsible gambling page.