CalculatorsUpdated 21 Jul 20262 min read
Arbitrage Calculator
Enter the price for each outcome — usually from different bookmakers — and this splits your stake so every result pays the same.
Implied probabilities sum to 95.24% — below 100%, so the book is beatable. Staking as split below returns 105.00 whichever outcome lands.
| Outcome | Odds | Stake | Returns if it lands |
|---|---|---|---|
| Outcome A | 2.10 | 50.00 | 105.00 |
| Outcome B | 2.10 | 50.00 | 105.00 |
Every row returns the same amount by design — that is what makes the outcome risk-free. What it is not is free money: arbs are small, short-lived, and the accounts that take them get limited quickly.
The whole test in one line#
Add up 1 ÷ odds for every outcome. Below 100% and you can cover the market for less than it pays. At or above 100%, you cannot, and the excess is exactly the bookmaker's margin.
| Book | Implied sum | What it means |
|---|---|---|
| One bookmaker, 1X2 | 105–108% | Guaranteed loss to cover |
| Best prices across books | 99–100% | Break-even, no edge |
| Two books disagreeing | 98% | Arbitrage: +2% |
How the stakes are worked out#
Each outcome gets a share of the stake proportional to its implied probability, so that the payout is identical whichever one lands:
stake on outcome i = total × (1 ÷ oddsi) ÷ (sum of all 1 ÷ odds)
The return is then total ÷ the implied sum, for every outcome. If the sum is 0.98, you get back 102% of your stake no matter what happens.
Arbitrage and value betting are different activities. A value bet takes a price better than the true probability and accepts variance. An arb takes no view on probability at all — it exploits a pricing disagreement and carries no variance, only execution risk. Neither requires the other.
What the calculator can't price#
The maths is trivial; the practical risks aren't, and they're what turns a 2% arb into a loss:
- The price moves before your second leg lands. You are then one-sided on a bet you didn't want.
- One bookmaker voids or limits the bet. You keep the other leg, exposed.
- Different settlement rules. Two books can disagree on what a market covers — extra time, abandonments, own goals — and settle the "same" bet differently.
- Account limits. This is the real ceiling. Bookmakers identify arb accounts quickly and cut stakes to pennies.
The full guide to arbitrage betting covers what living with those constraints actually looks like.
A useful second job#
Even with no arb in sight, this tool measures a market. Enter one bookmaker's three 1X2 prices: the implied sum is that book's overround, and how far above 100% it sits tells you how expensive it is to bet there. Comparing that number across bookmakers is a faster read on who prices sharply than any review site.
Related
- Arbitrage Betting: Real, Legal, and Mostly Not Worth It
- Fair Odds: What the Bookmaker's Margin Hides
- What Is Value Betting? A Plain-English Guide
- Expected Value in Betting: The Number That Decides Everything
- Fair Odds Calculator — Remove the Bookmaker Margin from Any 1X2 Book
- Odds Converter — Decimal, Fractional, American & Implied Probability
- Expected Value Calculator — Is Your Bet +EV?
Frequently asked questions
How do you calculate an arbitrage bet?
Convert every outcome's odds to implied probability (1 ÷ odds) and add them up. If the total is below 1, an arbitrage exists. Split your stake in proportion to each implied probability and every outcome returns the same amount — total stake ÷ the sum.
What is a good arbitrage percentage?
Real arbs are small: 1–2% is typical and anything above 5% usually means a price is about to be voided, a line has moved, or you have misread the market. Treat a large apparent arb as a mistake to check rather than a windfall.
Is arbitrage betting legal?
Yes — you are placing ordinary bets at ordinary prices. It is not, however, against the rules for bookmakers to object: accounts that consistently take arbs get stake-limited or closed, which is the practical constraint on the strategy rather than any legal one.
Why does my calculator show a guaranteed loss?
Because the implied probabilities sum above 100%, which is the normal state of any single bookmaker's book. That excess is the margin. Covering every outcome inside one margin-carrying book always loses — arbitrage needs prices from different books disagreeing enough to close the gap.