Guide · 7 min read
Accumulator bets explained: odds, returns and the rules that matter
An accumulator, or acca, puts several selections on one bet slip and multiplies their odds. One wrong pick and the whole slip loses. This guide shows how to work out the odds and the payout yourself, how likely an acca really is to land, what happens when a leg is void, and what every extra leg costs you on average.
Updated 22 October 2026
Contents
What an accumulator is
An accumulator (acca, multiple or parlay in the US) combines two or more selections from different events in a single bet. It only wins if every selection, or "leg", wins. The names follow the number of legs:
- Double: two selections.
- Treble: three selections.
- Four-fold, five-fold and so on: four or more selections. Anything from four legs up is usually just called an acca.
On the bet slip you enter one stake for the whole acca. That is the difference from a system bet such as a Trixie or a Yankee, which splits your selections into several smaller accas, each with its own stake.
Working out the odds and returns
The acca odds are the decimal odds of every leg multiplied together:
acca odds = odds 1 × odds 2 × … × odds n
return = stake × acca odds · profit = return − stake
Three Saturday football picks: a home win at 1.80, over 2.5 goals in another match at 2.00 and an away win in a third at 1.50.
Acca odds: 1.80 × 2.00 × 1.50 = 5.40. A €10 stake returns 10 × 5.40 = €54.00 if all three win, a profit of €44.00. If any one of them loses, the return is €0.
The maths is the same as placing the first leg as a single and rolling the whole return onto the next leg, and so on. That is where the name comes from: the winnings accumulate. If you use fractional odds, convert them first (5/4 is 2.25 in decimal); odds formats shows how. Reading the potential return on a real slip is covered in how to read a bet slip.
The chance that every leg wins
The probabilities multiply too. Each set of odds implies a probability of roughly 1/odds (a little less in reality, because the bookmaker's margin is built in; see implied probability). For the treble above:
1/1.80 × 1/2.00 × 1/1.50 = 0.556 × 0.500 × 0.667 ≈ 0.185
Even on the bookmaker's own numbers, the treble lands about 18.5% of the time, a little less than one in five. Three picks that each feel likely add up to a bet that usually loses. Add two more legs at 2.00 and the chance falls to about 4.6%, or roughly one in 22. That is not a reason never to play an acca, but it is the number to keep in mind when choosing the stake.
Rules that change the payout
A few rules in the bookmaker's terms decide whether an acca can be placed and what it pays:
- Related selections. Most bookmakers won't let you combine two legs from the same match in a normal acca (a team to win and over 2.5 goals, for example), because the outcomes depend on each other. Same-game combinations are sold as a separate product with its own pricing; see bet builders explained.
- Maximum payout. Every bookmaker caps the amount a single bet can win. Long accas at high odds can hit that cap, and anything above it is simply not paid.
- Dead heats. If one leg ends in a tie for a place (common in golf and racing), that leg is settled at reduced odds and the whole acca pays less. See dead heat rules.
- Settlement period. Each leg is settled on its own market rules. A football 1X2 leg counts regular time only; a "to qualify" leg includes extra time and penalties. More in overtime betting rules.
When a leg is void
If a match is postponed or abandoned, or a leg is voided for another reason, most bookmakers settle that leg at odds of 1.00 and let the rest of the acca run. The acca odds drop accordingly.
In the treble above, if the over 2.5 leg is voided, the slip becomes a double at 1.80 × 1.50 = 2.70, so €10 returns at most €27 instead of €54. If only one leg is left, it is settled like a single. If every leg is void, the stake comes back. How long a bookmaker waits before voiding a postponed match differs between bookmakers, as does the treatment of tennis retirements; see abandoned and postponed matches and tennis retirement rules.
The margin multiplies
Every price contains the bookmaker's margin, and in an acca those margins multiply along with the odds. With a 5% margin on each leg, the effective margin of the slip is 1.05 to the power of the number of legs:
| Legs | Effective margin | Average return to players | Expected loss per €100 |
|---|---|---|---|
| 1 (single) | 5.0% | 95.2% | €4.76 |
| 2 (double) | 10.3% | 90.7% | €9.30 |
| 3 (treble) | 15.8% | 86.4% | €13.62 |
| 4 | 21.6% | 82.3% | €17.73 |
| 5 | 27.6% | 78.4% | €21.65 |
The table assumes fairly priced picks apart from the margin. Picking well improves each leg, but no pick removes the margin itself. The full table up to ten legs, and why near misses feel closer than they are, is in why accumulators lose; how to work out a market's margin is in bookmaker margin and overround.
Acca boosts and acca insurance
Accas are the most promoted bet type in the industry. Two offers come up again and again:
- Acca boost: extra winnings on accas with a minimum number of legs, for example +10% for five legs or more. On a five-fold at 2.00 per leg (32.00 in total), a 10% boost on the odds lifts the price to 35.20. With a 5% margin per leg, it would take a boost of about 27.6% to cancel the margin.
- Acca insurance: if exactly one leg lets you down, the stake comes back, usually as a free bet rather than cash. A free bet is worth less than cash, because the stake is not returned with the winnings; free bets shows what one is realistically worth.
Both improve the maths a little. Read the terms each time: minimum odds per leg, minimum legs, which markets qualify and whether the boost applies to the odds or only to the profit. More in odds boosts.
Singles, system bets and hedging
- Singles. The same three picks as three €10 singles carry the 5% margin once each, not compounded, and one wrong pick doesn't sink the others. The trade-off is a much smaller top payout.
- System bets. A Trixie, Yankee or "2 from 3" splits your picks into several smaller accas, so a single loser doesn't lose everything. It costs more stake for the same picks, and every line still carries the multiplied margin. See system bets explained.
- Hedging the last leg. When all but one leg have won, you can bet against the last leg elsewhere to lock in part of the return. Hedging an accumulator works through the stake formula and the cost; cash out vs hedging compares it with the bookmaker's cash-out offer.
Why sure bets are singles
A sure bet uses a price difference between bookmakers to cover every outcome of one market. That only works when each bet slip covers exactly one market, so sure bets are always placed as singles:
- Covering every combination is expensive. Two two-way matches already need four slips to cover in accas, two three-way matches need nine, and the best price for every combination would have to sit at the same bookmaker.
- Void rules differ. If one bookmaker voids a leg and another settles it, the cover no longer matches and part of your money is unprotected.
- The margin is multiplied, not avoided. A price edge of 1 to 2% disappears quickly once it is multiplied with the normal margin of other legs.
If you play accas for fun, know what each extra leg costs and keep the stake small.
Frequently asked questions
What is an accumulator bet?
An accumulator, or acca, is one bet that combines two or more selections from different events. The odds are multiplied together and the bet only wins if every selection wins. A double has two legs, a treble three, and anything from four legs up is usually just called an acca.
How do you work out accumulator odds?
Multiply the decimal odds of every leg. Picks at 1.80, 2.00 and 1.50 give 1.80 × 2.00 × 1.50 = 5.40, so a 10 euro stake returns 54 euros if all three win. Convert fractional odds to decimal first.
What happens if one leg of an accumulator is void?
At most bookmakers the void leg is settled at odds of 1.00 and the rest of the acca carries on at lower total odds. A treble with one void leg becomes a double. If every leg is void, the stake is returned. The exact rule is in each bookmaker's terms.
What is the difference between an accumulator and a system bet?
An accumulator is one bet with one stake that needs every leg to win. A system bet such as a Trixie or a Yankee splits the same picks into several smaller accumulators, each with its own stake, so you can still get a return if one or more picks lose.
Sources
- Wikipedia: Fixed-odds betting (accumulators and full-cover bets)
- Wikipedia: Parlay (gambling)
- UK Gambling Commission: public register of licensed operators
- Bookmakers' betting rules, sections on multiples and accumulators (void legs, related contingencies, maximum payouts)
As of October 2026. The worked examples are illustrations with the stated odds. Bookmakers' rules, odds and offers change; their current terms and betting rules always apply.
Not betting, legal or tax advice. 18+. Betting involves risk and no profit is guaranteed. Only bet money you can afford to lose. Our responsible gambling page lists free help, and the disclaimer applies.