Sure Bets & Arbitrage Calculator

What is a sure bet?

A sure bet is the betting name for arbitrage: backing every possible outcome of the same market at different bookmakers, at prices high enough that you get back more than you staked whichever outcome happens. In football that usually means a two-way market, such as over or under 2.5 goals or both teams to score, or a three-way market such as the full-time result: home, draw or away.

It works because bookmakers don't agree on prices. Each one sets its own odds, moves them at its own speed and builds in its own margin. Normally the margin wins: take the best price for every outcome across the whole market and you still pay something for the privilege. Once in a while one bookmaker is slow to react to news or to money, and its price on one outcome climbs high enough that, combined with the best prices elsewhere, the margin flips the other way. That gap is the sure bet.

The name oversells it. A sure bet removes the risk of the match result, not every risk. The return is only locked in if every leg is accepted at the price you saw, at the stake you wanted, and settled under the same rules. Bookmakers can and do move prices, cut stakes, void bets placed at obvious errors and restrict accounts that take arbitrage. The rest of this guide covers how the arithmetic works, how to place a sure bet carefully and what tends to go wrong.

How the arithmetic works

Every decimal price implies a probability: 1 divided by the odds. Odds of 2.00 imply 50% and odds of 4.00 imply 25%. At a single bookmaker the implied probabilities of all the outcomes of a market add up to more than 100%, typically 103–108% for a football match result. The excess is the bookmaker's margin.

To check for a sure bet, take the best price for each outcome from any bookmaker and add up the implied probabilities. Above 100% there is no arbitrage, and the excess is what the market still charges you; the calculator shows it as the margin. Below 100% there is a gap: the shortfall is how much the prices are paying above fair across the whole market.

Take over 2.5 goals at 1.72 at one bookmaker and under 2.5 goals at 2.50 at another. The implied probabilities are 58.14% and 40.00%, which add up to 98.14%. To get the same payout whatever happens, split the stake in proportion to the implied probabilities: stake on an outcome = total stake × (1 ÷ its odds) ÷ the sum of 1 ÷ odds. For a total of 100 that is 59.24 on over and 40.76 on under. Either way the payout is 101.90, a return of 1.90% on the 100 staked. That is the default example in the calculator above.

The same formula works for three outcomes. A home win at 2.10, a draw at 3.40 and an away win at 4.80, each at whichever bookmaker offers the best price for it, imply 47.62% + 29.41% + 20.83% = 97.86%. A total of 100 splits into 48.66, 30.05 and 21.29, and each outcome pays about 102.18. Notice how small these numbers are. Most real gaps are worth 0.5–3% of the stake, and anything much bigger usually means one of the prices is wrong or out of date.

How to find and place a sure bet, step by step

1. Compare the same market across bookmakers. You need the best price for every outcome of one market, at bookmakers where you already have funded accounts. Doing this by hand is slow, so most people who take arbitrage seriously use a scanner that compares many bookmakers every few seconds. Odds comparison pages, including the match pages on OddsFilter, show the spread of prices but are not fast enough to catch most gaps while they are open.
2. Confirm that it really is the same market. Check the line (over 2.5 is not over 2.25), the period (90 minutes plus stoppage time, or including extra time and penalties) and what each bookmaker does if the match is postponed or abandoned. A gap between two markets that only look alike is not arbitrage.
3. Recheck every price at the bookmaker. Open each bet slip and look at the price on offer now, not the one in a scanner or a feed. Enter those live prices in the calculator.
4. Work out the stakes. Enter the total you want to commit. You can round the stakes to whole units: round amounts draw less attention than 59.24, but rounding moves the payouts apart, so check that the lowest payout still beats the total staked.
5. Place the riskiest leg first. That is usually the price that is out of line with the rest of the market, at the bookmaker most likely to cut it or limit your stake. If that leg is refused or the price drops, you can walk away before committing to the others.
6. Place the other legs straight away and read every receipt. Check the accepted price and stake on each bet. If a leg went through at a lower price or a smaller stake, recalculate at once and decide whether to rebalance the others.
7. Record the bet. Write down each leg, price, stake and bookmaker. Arbitrage profits are small per bet, so fees, mistakes and the odd voided leg decide whether you are ahead over a month.

Why sure-bet gaps close fast

A gap exists because one price is out of step with the rest of the market, and markets correct that quickly. Sharp bookmakers and betting exchanges react to money within seconds. Soft bookmakers copy or follow those moves, some automatically and some by hand, and the slowest of them is where the gap comes from. Once it catches up, the gap is gone. On popular matches that can take less than a minute, and plenty of other bettors are watching the same prices with the same software.

There is a second reason. A price that sits far above the rest of the market is often not an opportunity but a mistake: a stale price after a team-news change, a line entered wrongly, or a market that settles under different rules. Those gaps look the biggest and are the most likely to be refused, cut or voided.

Our own data shows the same pattern. The odds on OddsFilter come from a data provider that refreshes pre-match prices every few hours, not every few seconds. When we scanned about 13,000 football markets kicking off in the next day and a half in October 2026, around 30 showed a gap above zero, and the biggest of them nearly always set one bookmaker's older price against a sharper bookmaker that had already moved. By the time a price that old reaches a screen, the gap behind it has usually closed. That is why this page has a calculator and no list: a list built from prices hours old would mostly show gaps that no longer exist.

The risks

Price moves between legs

Sure bets are placed one leg at a time, and the price on the second leg can drop while you place the first. In the example above, if the under price falls from 2.50 to 2.30 before you bet it, the same 40.76 returns 93.75. You would then win 1.89 if the match has three or more goals and lose 6.25 if it has fewer. You can rebalance with a bigger stake at the lower price or look for the price elsewhere, but the locked-in return has gone and you may finish with a small loss.

Voided legs and rule differences

If one leg is voided and the others stand, you no longer hold an arbitrage; you hold an ordinary bet. In the same example, if the over bet is voided and its 59.24 refunded, you are left with 40.76 on under at 2.50: 61.14 up overall if the match has fewer than three goals, 40.76 down if it has more. Legs get voided for many reasons: a postponed or abandoned match (bookmakers use different deadlines before they void), a bet struck after kick-off by mistake, or a market the bookmaker settles differently from the others.

Rule differences catch people out even when nothing is voided. A cup tie can be settled on 90 minutes at one bookmaker and including extra time and penalties at another, in a “to qualify” market. A market with a refund option, such as draw no bet or a whole-number goal line, does not pair cleanly with a market where the same result simply loses. Read the market rules at each bookmaker before you treat two prices as opposite sides of one bet.

Obvious-error rules

Most bookmakers' terms let them void a bet, or resettle it at a corrected price, when the odds were an obvious or “palpable” error. A price far above the rest of the market is exactly what those rules are written for, and the bookmaker decides what counts as obvious. If the error leg is cancelled after the match and your other legs have lost, the loss is yours. The gaps that look too good, such as 5% or more on a major league, deserve the most suspicion.

Stake limits and account restrictions

The bookmakers that offer out-of-line prices are the ones that most dislike arbitrage. Their risk systems spot accounts that bet odd amounts, only take prices above the rest of the market and never bet into the margin. The usual response is to cut maximum stakes, sometimes to a few pounds or euros (in the UK this is called gubbing), to withdraw promotions, or to close the account. A stake limit can also hit mid-bet: the first leg goes through at full stake and the second is only accepted at a fraction of it, leaving you unbalanced. Over time, the real cost of arbitrage is how fast it uses up bookmaker accounts.

Costs that eat the margin

A 1.5% gap disappears quickly. Exchange commission, often 2–5% of net winnings, deposit and withdrawal fees, currency conversion between accounts and tax where it applies can all cost more than the gap is worth. Count them before you call a sure bet a profit, and keep enough money at each bookmaker to place a leg the moment you need to, because moving money between accounts takes time the gap doesn't give you.

Sure bets vs value bets

Value betting is the other approach built on comparing prices across bookmakers. A sure bet backs every outcome so the result no longer matters; a value bet backs one outcome whose price is higher than its real chance justifies, and accepts that it can lose. Sure bets swing very little, but they are rare, small, close within minutes and get accounts limited quickly. Value bets turn up far more often and can earn more on average, but results swing, and you need hundreds of bets before the edge shows.

The two are closely linked. The out-of-line price at the heart of most sure bets is a value bet on its own; the other legs only exist to cancel the risk, and they cost part of the edge. Some bettors take just that one leg and accept the variance. Our value bets page lists football prices that beat Pinnacle's no-margin odds, with fair odds, edge %, and a public track record once enough bets have settled, and its guide explains the method and the variance that comes with it.