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Arbitrage / sure betEngine updated: Jun 2026

Sure Bet Calculator & Arbitrage Scanner (2026)

Enter the odds you found at each bookmaker and get the exact stake on every outcome that locks the same return whoever wins. Decimal, American or fractional. Scan live odds for real arbitrage right now.

Built and verified byEvgeniy Volkov·iGaming analyst

Sure bet calculator

Add an outcome for every result of the market (two for a tennis match, three for a 1X2 football market), enter the best price you found for each, and read the stakes below. The total implied probability tells you instantly whether the bet is a real sure bet.

Outcomes and odds

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Quick examples:

Result

Enter odds for at least two outcomes to see the stake split and whether a sure bet exists.

Live arbitrage scanner

Pull current head-to-head odds across bookmakers and surface markets where the best available prices add up to less than 100%. These are real opportunities from live data, not examples. Click one to load it straight into the calculator above.

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The arbitrage math

Three short formulas are all you need. No spreadsheet required.

Implied probability

P = 1 / decimal odds

Odds of 2.50 imply a 40% chance. This is the bookmaker's view of the outcome before margin.

Sure bet test

sum of (1 / odds) < 1

Add the implied probability of every outcome at its best price. Under 100% means a guaranteed profit is possible.

Stake split

stake = total x (1 / odds) / sum

Each stake is proportional to its implied probability, so every outcome returns the same amount.

Profit

profit = total / sum of (1 / odds) - total

A 2% margin on a 1,000 stake locks roughly 20 of profit no matter which result lands.

How to use this tool on ToolsGambling.com

  1. 1

    Find the best price for each outcome

    Compare the same market at two or more bookmakers. Take the highest odds available for each outcome.

  2. 2

    Enter the odds

    Type each price into the calculator in decimal, American or fractional format. The implied probability appears next to each one.

  3. 3

    Check the margin

    If the total implied probability is below 100%, the margin is positive and you have a sure bet.

  4. 4

    Copy the stakes

    Place the calculated stake at each bookmaker. Round them if you prefer round numbers.

  5. 5

    Re-check before you bet

    Odds move. Confirm both prices are still live at the bookmaker before placing the second leg.

What a sure bet actually is

A sure bet, also called an arbitrage or arb, happens when two bookmakers disagree enough about an event that you can back every outcome and still come out ahead. One book is too generous on the home win, another is too generous on the away win, and the gap between their prices is large enough to cover both bets with profit left over. It is not a system, a tip or a prediction. It is simple arithmetic on numbers that are already public.

The catch is that the gap is usually tiny, often one or two percent, and it closes within minutes as bookmakers adjust. That is why a calculator matters: you need the exact stake on each side, fast, before the prices move. This page gives you that split instantly and, with the live scanner, shows you where real gaps exist right now.

Why bettors use a sure bet calculator

It removes the guesswork from stakes

The hard part of an arb is not spotting it, it is sizing the bets so every outcome returns the same. Get the split wrong and your guaranteed profit turns into a loss on one side.

It works in any odds format

Bookmakers in the US quote American odds, UK shops quote fractions, and most of Europe uses decimals. The calculator converts all three so you can compare prices from anywhere.

It is honest about the margin

If the numbers do not arb, the tool says so plainly instead of dressing up a losing bet. A negative margin is the bookmaker overround, and no stake split can beat it.

It scales to three-way markets

Football 1X2 markets have three outcomes, and the maths is fiddlier than a two-way tennis line. Add an outcome and the split adjusts automatically.

How the calculator works under the hood

Each decimal price is turned into an implied probability by taking one divided by the odds. The tool adds those probabilities together. If the total is below one, the combined market is underpriced and an arbitrage exists. The stake on each outcome is then set in proportion to its implied probability, which is the only split that returns the same amount whichever result lands.

When you round stakes to whole units the per-outcome returns drift apart slightly, so the tool reports the worst-case return as your guaranteed figure rather than an optimistic average. Every number you see here is produced by the same tested function, so the calculator and the scanner always agree.

Using the free sure bet tool on ToolsGambling.com

On ToolsGambling.com you can use the sure bet calculator for free, just like all our other betting tools. There is no signup and no limit on calculations. Enter your odds, read the split, and if you want a second opinion on the underlying prices, cross-check them with the related calculators below.

Two worked examples

A two-way tennis arb

Bookmaker A prices Player 1 at 2.10, Bookmaker B prices Player 2 at 2.10. The implied probabilities are 47.6% each, totalling 95.2%, so the margin is 4.8%. On a 1,000 total stake you put 500 on each side and lock about 50 in profit whoever wins. That is a strong arb and, in practice, a rare one.

A three-way football arb

Best prices come to 3.10 on the home win, 3.60 on the draw and 2.60 on the away win. The implied probabilities add up to 98.5%, a 1.5% margin. The calculator splits a 1,000 stake into roughly 318, 274 and 379, each returning around 985 to 987, for about 15 guaranteed. Smaller margins like this are far more common than the tennis example.

Common mistakes that kill a sure bet

1.

Stale odds

The price you saw thirty seconds ago may already be gone. Always refresh both legs before staking, and place the harder-to-get leg first.

2.

Account limits

Bookmakers dislike arbers and will limit or close accounts that only bet sure bets. Spreading turnover and mixing in normal bets matters if you do this regularly.

3.

Wrong market match

The two prices must cover the exact same market. A full-time result is not the same as a result-after-90-minutes line, and mixing them voids the arb.

4.

Forgetting the draw

On three-way markets it is easy to back only two outcomes. If the draw lands you lose. Cover every outcome the market offers.

5.

Ignoring bet limits and minimums

If one leg has a low maximum stake, you cannot place the full calculated amount and your real margin shrinks. Check limits before you size the bet.

Sure bet glossary

Arbitrage
Backing every outcome of an event at prices that guarantee a profit regardless of the result.
Implied probability
The chance an outcome happens according to its odds, found as one divided by the decimal price.
Overround
The amount a market sits above 100%. It is the bookmaker's built-in margin and the opposite of an arb.
Margin
On this page, how far below 100% the best combined prices sit. The bigger it is, the larger your guaranteed profit.
Two-way and three-way
A market with two outcomes (most tennis or money-line bets) or three (football 1X2, where the draw counts).
Stake split
Dividing your total stake across outcomes so each returns the same amount.
Sharp bookmaker
A book with low margins and high limits, like Pinnacle, whose prices rarely create arbs but rarely lie either.

A note on responsible betting

Arbitrage looks risk-free on paper, but limits, mistakes and stale prices make it far from guaranteed in practice. Never stake money you cannot afford to lose, and treat betting as entertainment rather than income. If it stops being fun, take a break. Support is available at BeGambleAware.org.

FAQ

Sure bet calculator FAQ

A sure bet, or arbitrage, is when the best available odds for every outcome of an event add up to less than 100% implied probability. Backing all outcomes in the right proportion then guarantees a profit whichever result lands.
Placing bets at different bookmakers is legal in regulated markets. However, bookmakers are private companies and may limit or close accounts they suspect of arbing. It is allowed, but not always welcomed.
Margins are usually small, often one to three percent of the stake, and large bankrolls are needed for meaningful returns. The bigger risk is account limits rather than losing individual bets.
Use whichever your bookmaker shows. The calculator accepts decimal, American and fractional odds and converts them internally, so you can mix bookmakers from different regions.
Usually because a price moved before the second leg was placed, the markets did not match exactly, or one leg was limited. Always re-check both prices and place the harder leg first.
Each stake is set in proportion to its implied probability. The calculator does this automatically so every outcome returns the same amount. Rounding stakes is optional and slightly changes the per-outcome return.
A sure bet covers every outcome for a guaranteed profit. A value bet backs a single outcome you believe is underpriced, which has positive expected value but can still lose. The value bet calculator covers that case.
Yes. It reads current head-to-head odds across bookmakers and only lists markets that genuinely arb. If nothing shows, there is no clean sure bet at that moment, which is the normal state most of the time.
Yes. Use the embed button to copy an iframe snippet. It carries a link back to ToolsGambling and resizes itself to fit your page.
Reviewed by
Evgeniy Volkov

Evgeniy Volkov

Verified Expert
Fullstack Developer

Fullstack developer with a background in mathematics. I build the calculators and game-style tools on ToolsGambling with Pixi.js and modern web tech, and every result uses transparent probability formulas you can verify yourself.

EducationMathematics
SpecializationiGaming
StatusActive
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