How does an accumulator (parlay) work?
Depending on the country it is called an accumulator, a parlay, a multiple or a combo: it is always the same bet. An accumulator puts several bets, known as selections, into one. For it to come in, every selection must be right. One wrong, and the whole thing is lost.
The odds multiply. Invented example: 1.50 × 1.60 × 1.70 = 4.08. That higher price is what attracts people. But the price is only half the story.
Why does the chance of getting everything right fall so fast?
The chances multiply too. Take selections that each have a 70% chance of coming in, a figure invented for the example.
| Selections | Sum | Chance everything comes in |
|---|---|---|
| 1 | 70% | 70% |
| 2 | 0.70 × 0.70 | 49% |
| 3 | 0.70 × 0.70 × 0.70 | 34% |
| 4 | 0.70 to the power 4 | 24% |
| 5 | 0.70 to the power 5 | 17% |
| 6 | 0.70 to the power 6 | 12% |
With four selections, roughly one accumulator in four comes in. Yet each selection on its own looked "likely". The accumulation changes everything.
Does the bookmaker margin add up with every match?
Yes. Every price contains its margin (see our guide to reading odds). In an accumulator, those margins multiply too.
Invented example: with a 5% margin on each price, three selections give a cumulative margin of about 16% (1.05 × 1.05 × 1.05 = 1.16). The more selections you add, the further the accumulator's price drifts from the fair price.
Can you combine two bets from the same match?
Some sites offer it. Be careful: bets from the same match are linked. If a match is open, "over 2.5 goals" and "both teams to score" often go together. Multiplying their chances as if they were independent gives a wrong result.
The simple sum, multiplying, only works for events that do not depend on each other, for example matches in different leagues.
A full example: from the odds to the verdict
Back to the 4.08 accumulator. The division 1 ÷ 4.08 gives 24.5%: that is the chance the price contains.
- First set of estimates: 70%, 65% and 60%. Multiply: 0.70 × 0.65 × 0.60 = 27%. That is almost 3 points above 24.5%, provided those estimates are right.
- Second set of estimates: 62%, 60% and 58%. Multiply: 0.62 × 0.60 × 0.58 = 22%. That is below 24.5%: the accumulator is poorly priced.
Same price, two verdicts. Everything depends on the chances you calculate for each match, which is why they deserve careful estimates.
How do you read an accumulator with method?
- Put a number on each selection. Write down the chance of each one, then multiply. The result is the chance of the accumulator.
- Compare it with the accumulator's price. Divide 1 by the odds: 1 ÷ 4.08 = 24.5%. If the chance you calculate is lower, the accumulator is poorly priced.
- Keep the number of selections low. Each addition lowers the chance and raises the cumulative margin.
Losing an accumulator on its last selection is frustrating, but it is exactly what the sum predicts. It is not exceptional bad luck: it is how accumulators normally behave.
IASHARK also publishes its football combos of the day before the matches. They follow the same sum as every other one.
Frequently asked questions
What happens if a match in the accumulator is postponed?
Rules vary from one site to another. Read the rules before choosing, because a postponed match is not handled the same way everywhere.
How many selections can you put in an accumulator?
It depends on the site. But every selection added lowers the chance of getting everything right.
How do you work out the chance of an accumulator?
You multiply the chance of each selection. Three selections at 70% give 0.70 × 0.70 × 0.70, about 34%.
Is an accumulator better than several single bets?
It does not change the chance of each match: it stacks them. It is one bet with a lower chance and a higher price.
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