If you're getting into sports arbitrage, the surebet calculator is the most important tool in your operation. Without it, you can't know if an opportunity is real, how much to stake on each outcome, or what your exact profit will be.
This guide covers how surebet calculators work, how to use one in practice, and what separates the basic tools from the more complete ones.
A surebet calculator tells you how much to stake on each outcome of an event to guarantee a profit regardless of the result. You input the odds from different books, and it outputs the exact amounts to bet on each side.
The underlying logic is simple: if the sum of the reciprocals of the odds is less than 1, you have a surebet. The difference from 1 is your profit margin.
Formula:
Sum = (1 / odds A) + (1 / odds B) + (1 / odds C) + ...
Sum < 1 → you have a surebetSum = 1 → pure break-even (no profit)Sum > 1 → no surebetPractical example — football match (3 markets):
| Outcome | Odds | Calculation |
|---|---|---|
| Team A wins | 2.10 | 1 / 2.10 = 0.476 |
| Draw | 4.00 | 1 / 4.00 = 0.250 |
| Team B wins | 3.80 | 1 / 3.80 = 0.263 |
Sum = 0.476 + 0.250 + 0.263 = 0.989
0.989 < 1 → Surebet found! Guaranteed profit of 1.1% of total stake.
You have a surebet — now you need to know how much to bet on each outcome. The formula is:
Stake = (Designated bankroll × (1 / odds)) / Sum of fractions
Example with $500 bankroll:
| Outcome | Odds | Stake |
|---|---|---|
| Team A wins | 2.10 | 500 × 0.476 / 0.989 = $240.65 |
| Draw | 4.00 | 500 × 0.250 / 0.989 = $126.39 |
| Team B wins | 3.80 | 500 × 0.263 / 0.989 = $132.97 |
Total staked: $500
Returns: - If A wins: 240.65 × 2.10 = $504.97 (+$4.97) - If draw: 126.39 × 4.00 = $505.56 (+$5.56) - If B wins: 132.97 × 3.80 = $505.29 (+$5.29)
Guaranteed profit between $4.97 and $5.56 on this event — roughly 1% return on capital.
Tennis has only two outcomes, which simplifies the calculation. A practical example:
Sum = 1/2.05 + 1/2.15 = 0.4878 + 0.4651 = 0.9529
Surebet with 4.71% profit margin. With $500 bankroll:
Guaranteed profit: ~$25
Let's walk through the full process from spotting the odds to placing the bets, so you can do this yourself without relying on any tool.
Suppose you're looking at a football match: Liverpool vs Arsenal. You check three bookmakers and find:
| Outcome | Book A | Book B | Book C |
|---|---|---|---|
| Liverpool | 1.95 | 1.90 | 1.88 |
| Draw | 3.70 | 3.80 | 3.60 |
| Arsenal | 4.20 | 4.00 | 4.30 |
Pick the highest available odds for each outcome: Liverpool @ 1.95 (Book A), Draw @ 3.80 (Book B), Arsenal @ 4.30 (Book C).
For each outcome, divide 1 by the decimal odds:
0.5128 + 0.2632 + 0.2326 = 1.0086
Since 1.0086 > 1, this is not a surebet. The margin is against you. Move on to another event.
Now suppose odds shift and you see: Liverpool @ 2.20, Draw @ 3.90, Arsenal @ 4.50.
Sum = 0.4545 + 0.2564 + 0.2222 = 0.9331
0.9331 < 1 → Surebet! Profit margin = 1 − 0.9331 = 6.69%
With a $1,000 bankroll:
Guaranteed profit: ~$70 regardless of outcome. That's a strong arbitrage opportunity.
Surebet calculations use decimal odds, but you'll encounter fractional (UK) and American (moneyline) odds too. Here's how to convert them.
Decimal = (numerator / denominator) + 1
Example: 6/4 → (6/4) + 1 = 1.5 + 1 = 2.50
You find these moneyline odds on a tennis match: Player A @ +110, Player B @ +120.
Sum = 1/2.10 + 1/2.20 = 0.4762 + 0.4545 = 0.9307 → Surebet with 6.93% margin. Always convert to decimal before running the surebet formula.
The 99BettingTips Surebet Calculator handles all the math for you. Here's how to use it:
The calculator also works with fractional and American odds — just select the format before entering. It converts automatically behind the scenes.
If you're distributing your stake across multiple selections in the same event (rather than different books), check out our Dutching Calculator instead. And to understand how much margin the bookmaker is building into their odds, use our Overround Calculator.
Free options: - Surebet Calculator — one of the old references, still useful - Odds Calculator — quick calculation for 2 and 3-way markets - OddsJam (paid) — scanner with built-in calculator - RebelBetting (paid, trial available) — scanner + calculator combo
What to look for in a calculator: - Support for 2, 3, and multi-way markets - Automatic stake calculation - Profit margin percentage display - Ability to adjust total stake amount
Calculators are for when you've already identified an opportunity and need to know the exact amounts to bet. They confirm whether the opportunity is real and what your profit will be.
Scanners find the opportunities automatically, checking odds across dozens of books in real time. They tell you where the arbitrage is; calculators tell you how much to bet.
In practice, you use both together: 1. The scanner identifies a potential surebet 2. The calculator confirms the amounts and validates whether the book's maximum stake will accept your position
Never fully trust a scanner without verifying. Odds change fast and scanners can show opportunities that have already closed.
Latency: The odds you saw on the scanner may no longer be available by the time you calculate. Speed is essential.
Limited stakes: The calculator may tell you to bet $300 on one outcome, but the book only accepts $50. That destroys the surebet because you can no longer cover all outcomes proportionally.
Input errors: If you enter the wrong odds, all calculations are wrong. Always verify twice before placing bets.
Very low margins: A 0.3% surebet may look good on paper, but after deposit/withdrawal fees and odds slippage, it can turn into a loss.
A surebet (or arbitrage bet) is a situation where the odds across different bookmakers are high enough that you can bet on all possible outcomes and guarantee a profit regardless of the result. This happens when the sum of the implied probabilities (1 ÷ odds for each outcome) is less than 1.
You need funds spread across at least 2–3 bookmaker accounts. A practical starting bankroll is $500–$1,000. Since surebet margins are typically 0.5–5%, you need decent volume to make meaningful returns. A $500 bankroll on a 2% surebet earns roughly $10 per opportunity.
Yes, many bookmakers restrict or close accounts that consistently bet on arbitrage opportunities. They identify arbers through patterns like always betting at maximum odds, placing unusual stake amounts, or only betting when odds are higher than the market average. Using multiple books and rounding your stakes to common amounts can help reduce detection.
Surebetting involves betting on all outcomes across different bookmakers to guarantee profit. Dutching involves distributing your stake across multiple selections at the same bookmaker to reduce variance — but you still lose if none of your selections win. Surebets are risk-free; dutching is a risk-management strategy.
Very fast. Arbitrage opportunities typically last seconds to a few minutes before odds adjust. By the time a scanner alerts you, other arbers are already placing bets, which moves the lines. Pre-load your bookmaker accounts and have them open and logged in so you can place all legs of the surebet within 30 seconds.
A surebet calculator is a simple tool in theory, but essential in practice. Without one, you're working blind. With one, you have clarity on how much to stake, what profit to expect, and whether the opportunity is real.
Always use it before betting. Always verify twice. And remember — the profit per operation is small. That's why consistency and discipline matter more than chasing the perfect opportunity.
Educational content. The calculators and scanners mentioned are reference tools. We do not recommend or guarantee results from any arbitrage platform.
Use these tools to find and size surebets: