Level 2 · Markets · Lesson 9 of 17
What is an accumulator? Accas and parlays explained
An accumulator, or acca (called a parlay in the US), is a single bet that links several selections together. The odds are multiplied, so the potential return grows quickly, but every selection must win. If one leg loses, the whole bet loses.
18+ 18+ only. Betting involves risk: never bet more than you can afford to lose. Nothing here is a guarantee of winning.
In this guide
How an accumulator works
You pick two or more selections from different matches and combine them on one bet slip. Two selections make a double, three a treble, four a fourfold, and so on. The total odds are the individual odds multiplied together.
Acca odds = odds 1 × odds 2 × odds 3 × …
Odds: 1.80 × 1.80 × 1.80 × 1.80 = 10.50 (10.4976)
£10 stake: return = £10 × 10.4976 = £104.98, profit £94.98
If any one of the four legs loses, you lose the whole £10.
That looks attractive: four "slight favourites" and the money multiplies by ten. The catch is what happens to the chance of winning.
The probability drop: why accas rarely land
The chances multiply too, and probabilities below 100% shrink fast when you multiply them.
Each leg at 1.80 implies 1 ÷ 1.80 = 55.6%.
Raw implied chance of all four = 0.556 × 0.556 × 0.556 × 0.556 = 9.5%
But the price includes a margin. If the fair price of each leg is 1.90 (52.6%):
Real chance of all four = 0.526⁴ = 7.7%
If each leg is really a coin flip (50%): 0.50⁴ = 6.25%
So the acca lands about once in 10 to 16 attempts, not "most weekends".
| Legs at 1.80 | Total odds | Raw implied chance | Chance if each leg is 52.6% |
|---|---|---|---|
| 1 (single) | 1.80 | 55.6% | 52.6% |
| 2 (double) | 3.24 | 30.9% | 27.7% |
| 3 (treble) | 5.83 | 17.1% | 14.6% |
| 4 (fourfold) | 10.50 | 9.5% | 7.7% |
| 6 | 34.01 | 2.9% | 2.1% |
Every leg you add makes the bet much less likely to win. A six-leg acca of reasonable favourites wins about once in every 47 attempts at the real chances above.
Margin compounding: the hidden cost
Each leg carries the bookmaker's margin, and in an accumulator those margins multiply too. That's why bookmakers love accas.
Using the example above, the fair price of each leg is 1.90 but you're paid 1.80. Per leg, every £1 staked is expected to return 0.526 × 1.80 = £0.947, a cost of about 5%. Across four legs:
Expected return per £1, single: 0.526 × 1.80 = £0.947 (−5.3%)
Expected return per £1, fourfold: 0.947⁴ = £0.806 (−19.4%)
Fair fourfold price: 1.90⁴ = 13.03; price you get: 10.50
In other words, a fourfold of 5%-margin legs costs you around 19% of your stake on average, almost four times as much as a single. This is the plain truth about accumulators: they're fun, but most acca bettors lose over time, and the more legs, the bigger the built-in loss. Treat an acca as a small entertainment stake, not a plan.
Calculate your acca return
Enter your stake and odds to see the total odds and potential return:
System bets: Trixie, Yankee and friends
System bets (also called full-cover bets) split your stake across every combination of your selections, so you can still get a return if one or more legs lose. You pay for that cover with a bigger total stake.
| Bet | Selections | Bets | Made up of |
|---|---|---|---|
| Trixie | 3 | 4 | 3 doubles + 1 treble |
| Patent | 3 | 7 | 3 singles + 3 doubles + 1 treble |
| Yankee | 4 | 11 | 6 doubles + 4 trebles + 1 fourfold |
| Lucky 15 | 4 | 15 | 4 singles + a Yankee |
Total stake = 4 bets × £1 = £4
All three win: each double returns £1 × 2.00 × 2.00 = £4 (×3 = £12), the treble returns £1 × 8.00 = £8. Total = £20.00, profit £16.00
Two win: only one double wins: £1 × 4.00 = £4.00. You get your stake back, profit £0
One or none win: return £0, you lose £4
System bets soften the blow of one losing leg, but they don't remove the margin. You're still placing several multiples, each with its own compounded edge for the bookmaker.
Acca insurance and boosts
Bookmakers often promote accas with extras:
- Acca insurance: if one leg loses, your stake is refunded, usually as a free bet and up to a maximum. A free bet usually returns only the winnings, not the stake, so it's worth less than cash.
- Acca boosts: the winnings are increased by a percentage for accas with enough legs, often 5 or more.
- Minimum odds per leg and minimum legs: offers usually require each leg to be at or above a set price.
These offers reduce the bookmaker's edge a little, but rarely enough to make a long acca a good bet. Read the terms on our bonuses page, and see how offers compare between bookmakers.
Common acca mistakes
- Adding "safe" legs. A 1.20 favourite still loses about one time in six on raw prices. It barely raises your payout but cuts the chance of winning.
- Too many legs. Every extra leg multiplies the cost. Two or three well-researched legs beat eight guesses.
- Linking related outcomes. Bookmakers usually block related selections in the same match (for example "team wins" and "team scores"), or price them as a bet builder.
- Forgetting settlement rules. A draw no bet leg that ends level, or a void leg, is usually counted at 1.00; the acca continues with fewer legs.
- Chasing a big payout. Don't increase stakes to win back a losing acca. Keep each acca to a small, fixed amount.
Accas vs singles
| Single | Accumulator | |
|---|---|---|
| Chance of winning | Higher | Much lower |
| Payout | Smaller | Bigger |
| Margin cost | One margin | Margins multiplied |
| Best for | Steady, measured betting | Small fun stakes |
If you want to test your own ideas over time, singles tell you much more about whether your picks are good, because one bad leg can't hide five good ones. Start with markets you understand, such as 1X2 or BTTS, and look at today's predictions for ideas.
Frequently asked questions
What is an accumulator bet?
An accumulator is one bet that combines two or more selections. The odds are multiplied together, and every selection must win for the bet to pay out. In the US it's called a parlay.
How are accumulator odds calculated?
Multiply the decimal odds of each leg. Four legs at 1.80 give 1.80 × 1.80 × 1.80 × 1.80 = 10.50, so a £10 stake returns about £104.98.
What happens if one leg of an acca is void?
The void leg is usually treated as odds of 1.00 and removed. The accumulator carries on with the remaining legs, at lower total odds.
What is the difference between a parlay and an accumulator?
Nothing. Parlay is the US name and accumulator (or acca) is the UK name for the same bet: several selections combined into one, with the odds multiplied.
Are accumulators worth it?
For most bettors, accumulators lose more over time than singles, because the bookmaker's margin is multiplied with every leg. They can be fun with a small stake, but they're not a way to make money.
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