How to calculate a sure bet and size the stakes
Two formulas: one tells you whether an arbitrage exists, the other tells you how much to put on each outcome. Both are arithmetic you can check by hand.
Step one: does an arbitrage exist?
Convert each best price to its implied chance and add them:
margin = 1÷odds₁ + 1÷odds₂ + … + 1÷oddsn
If the total is below 1.0, an arbitrage exists. If it is above, it does not — and no staking plan will rescue it.
Your profit percentage is:
profit % = (1 ÷ margin − 1) × 100
A margin of 0.9707 gives (1 ÷ 0.9707 − 1) × 100 = 3.02%.
Step two: how much on each outcome?
The stakes must be sized so that every outcome pays back the same amount. Otherwise you are still betting on a result.
stakei = total × (1 ÷ oddsi) ÷ margin
On ₦100,000 with odds of 2.10 / 3.90 / 4.20 and a margin of 0.9707:
- Home: 100,000 × (1÷2.10) ÷ 0.9707 = ₦49,057
- Draw: 100,000 × (1÷3.90) ÷ 0.9707 = ₦26,415
- Away: 100,000 × (1÷4.20) ÷ 0.9707 = ₦24,528
Check it: 49,057 × 2.10 = 103,019. 26,415 × 3.90 = 103,019. 24,528 × 4.20 = 103,019. Every outcome returns the same, and every outcome returns more than the ₦100,000 staked.
The step most calculators skip: rounding
No bookmaker accepts ₦49,057.34. Real stakes get rounded, and rounding breaks the equal-return property the whole thing depends on.
On a healthy 3% edge that barely matters. On a thin one it can turn a profit into a loss. A real example: a three-way at 1.50 / 5.10 / 7.72 shows a nominal +0.55%. Rounded to the nearest ₦5 on a ₦1,000 stake, the split becomes 675 / 195 / 130 and the true return is −₦5.50. The nominal number said profit; the placeable number was a loss.
So after rounding, always re-check the worst case:
guaranteed = min(stakei × oddsi) − total staked
If that is not positive, the bet is not worth placing however good the percentage looked. My Sure Odds runs this check on every opportunity before showing it, and discards the ones that fail.
Two-outcome markets
The same formulas apply with two terms instead of three. Tennis, and any market with no draw, works out simpler:
Odds of 2.10 and 2.05 give 1÷2.10 + 1÷2.05 = 0.4762 + 0.4878 = 0.9640, a 3.73% edge. Stakes of ₦49,398 and ₦50,602 return ₦103,735 either way.
Common questions
What is a good arbitrage percentage?
Most genuine opportunities sit between 0.5% and 3%. Below about 0.5% the edge rarely survives rounding and currency conversion. Above 10% it is usually a mistake — a stale price, a mismatched fixture, or two markets with different settlement rules.
Do I need to round my stakes?
Yes — bookmakers accept whole amounts, often in set increments. The important part is re-checking the worst-case return afterwards, because rounding can cost more than the edge on a thin arbitrage.
Why are the stakes different sizes?
Because the odds are different. The outcome with the shortest price needs the largest stake to return the same amount as the others. Splitting evenly leaves you exposed to whichever result is underfunded.
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