Accumulator Calculator
Enter the odds of each selection and your stake: the calculator shows the combined odds, potential return, net result and the probability implied by those odds. If the bet slip is already being settled, you can mark any leg as void, half won, half lost or lost.
It also works out what a bet slip does not show: how much margin has built up in the acca because of the number of legs, and what acca bonus would be needed to cover it.
Work out an acca from its odds
Choose between 2 and 10 selections and enter their odds. The “open” status is for a leg that has not been settled yet or has won in full. The margin and bonus fields are optional: they are there to assess the slip before you place it.
Inputs
Results update automatically. Odds can be entered as 1.85 or 1,85, and thousands separators are accepted in the stake. Statuses are only needed for legs that have already been settled; margin and bonus do not change the return itself — they are used to assess the slip.
Result
Enter the odds and the result appears automatically.
How accumulator odds are calculated
For an ordinary unsettled slip, the decimal odds are multiplied together.
K = K₁ × K₂ × … × KₙReturn = stake × KNet result = return − stakeImplied probability = 100 / KFor example, 1.70 × 1.85 × 2.10 = 6.6045. A stake of 100 returns 660.45 if all three selections win, a net result of +560.45, and the implied probability is 15.14%.
That probability is a price reference, not a prediction: every price carries the bookmaker’s margin, and outcomes may be correlated. To turn a single price into a percentage, use the odds to probability calculator.
Why the margin compounds in an acca
Each extra selection brings its own mark-up into the slip, and these multiply. The expected return of an n-fold accumulator is (1 / (1 + margin))ⁿ of the stake.
| Selections on the slip | 3% margin per selection | 5% margin per selection | 7% margin per selection |
|---|---|---|---|
| 1 (single) | 2.91% | 4.76% | 6.54% |
| 2 | 5.74% | 9.30% | 12.66% |
| 3 | 8.49% | 13.62% | 18.37% |
| 4 | 11.15% | 17.73% | 23.71% |
| 5 | 13.74% | 21.65% | 28.70% |
| 7 | 18.69% | 28.93% | 37.73% |
| 10 | 25.59% | 38.61% | 49.17% |
The table shows the share of the stake the bookmaker keeps on average at the given margin per selection. A single on a 5% market returns 95.24% of the stake on average; a five-fold of such selections returns 78.35%. This says nothing about a particular slip, which either wins in full or does not. It is the price at which you are betting over the long run.
It also explains why long accas rarely pay off: the mark-up grows along with the potential return. You can measure the margin of a specific market with the bookmaker margin calculator and enter it in the margin field above.
What acca bonus covers the margin
Bookmakers boost the return for the number of selections on a slip. Such a bonus is only good value when compared with the accumulated margin.
| Slip | Combined odds | Accumulated margin | Bonus on net profit for break-even |
|---|---|---|---|
| 3 selections at 1.80 | 5.83 | 13.62% | 19.03% |
| 5 selections at 1.80 | 18.90 | 21.65% | 29.17% |
| 7 selections at 1.80 | 61.22 | 28.93% | 41.39% |
| 5 selections at 2.00 | 32.00 | 21.65% | 28.52% |
Figures assume a 5% margin per selection. The bonus in the last column is the one at which the expected return exactly equals the stake. Anything lower leaves the slip negative in expectation; anything higher puts it in theoretical profit, provided the margin really is 5% and the outcomes are independent. Note that a bonus on net profit and a bonus on the whole return are different things: at the same percentage the second pays more. Enter the terms of your offer in the bonus fields and the calculator shows the expected return.
What happens when one leg is void
Under standard rules, a void leg is settled at odds of 1.00 and the rest of the selections stay in the acca. For 1.70 × 1.85 × 2.10, a void second leg gives a multiplier of 1.70 × 1.00 × 2.10 = 3.57: a stake of 100 returns 357 if the other selections win.
Odds boosts, minimum-selection requirements and special offers after a void may be settled under the operator’s own rules.
Half won and half lost
Quarter-line Asian handicaps and totals can settle partially. In acca arithmetic such a leg becomes an effective multiplier.
| Status | Leg multiplier | Meaning |
|---|---|---|
| Open | K | The odds count in full. |
| Void | 1.00 | The leg drops out of the combined multiplier. |
| Half won | (K + 1) / 2 | Half the stake wins at K, half is refunded. |
| Half lost | 0.50 | Half the stake loses, half is refunded. |
| Lost | 0 | An ordinary acca returns nothing. |
Worked accumulator examples
| Scenario | Calculation | Multiplier | Return on 100 |
|---|---|---|---|
| All three legs open | 1.70 × 1.85 × 2.10 | 6.6045 | 660.45 |
| Second leg void | 1.70 × 1.00 × 2.10 | 3.57 | 357.00 |
| Second leg half won | 1.70 × 1.425 × 2.10 | 5.08725 | 508.73 |
| Second leg half lost | 1.70 × 0.50 × 2.10 | 1.785 | 178.50 |
| One leg lost | leg multiplier = 0 | 0 | 0.00 |
Why combined odds are not a forecast
The value 1 / K is handy as a price reference, but it comes from the bookmaker’s odds: there is no independent view of team form, line-ups or other sporting factors in it. Correlation matters too: if outcomes are related, simply multiplying their probabilities is wrong.
In a Bet Builder or Same Game Parlay, the bookmaker prices related outcomes of one match together, so the published odds need not match the product of the individual prices. A Bet Builder slip is not an ordinary acca and should not be checked with this calculator.
Related tools
Bet payout
Return, net profit and implied probability for a single bet.
Odds converter
Decimal, fractional and American odds — handy when the legs are quoted in different formats.
All tools
Calculator catalogue: markets, odds, bankroll, bonuses and limits.
FAQ
How do I work out the combined odds of an acca?
Multiply the decimal odds of all selections. A void leg counts as 1.00, so it simply drops out of the product.
What happens if one selection is made void?
Its multiplier becomes 1.00, the other legs stay on the slip, and the return is recalculated from the remaining odds.
What happens if one leg loses?
An ordinary acca returns nothing, whatever happens to the other legs. A partial refund is only possible under a separate operator offer.
How is a half-won leg settled?
For a leg at odds K, the effective multiplier is (K + 1) / 2: half the stake plays at the odds and half is refunded.
Why is the margin higher on an acca than on a single?
Because the mark-ups of the selections multiply. At a 5% margin per selection, a single returns 95.24% of the stake on average, a treble 86.38% and a five-fold 78.35%.
Does a bonus for the number of selections make an acca worthwhile?
Only if it exceeds the accumulated margin. For five selections at 1.80 and a 5% margin, break-even needs a bonus of about 29.17% on net profit. A smaller bonus reduces the expected loss but does not remove it.
Is the probability of the acca winning an accurate forecast?
No. The calculator shows the inverse of the odds with the margin built in, not an independent sports model.
Does this calculation work for a Bet Builder?
Not always. The bookmaker prices outcomes within one match together, allowing for their correlation, so multiplying the individual prices can overstate the odds.