An accumulator, or acca, is a single bet on several selections where the return from each winning selection becomes the stake on the next. It is the bet behind most of the “£5 turned into £2,000” stories, and also behind a great many lost fivers. This guide shows how the return is calculated, what happens when a leg is void, how accas relate to Yankees and Lucky 15s, and why the bookmaker’s margin grows with every leg you add.
How the bet works
A double is two selections, a treble is three, and anything with four or more is an accumulator (four-fold, five-fold and so on). All the selections must win for the bet to pay. If one loses, the whole bet loses.
The return is worked out by multiplying the decimal odds of every selection together, then multiplying by the stake.
Return = stake × odds 1 × odds 2 × odds 3 …
Using fractions, convert each to a decimal first (divide the left number by the right and add 1). Take a £5 four-fold on four football teams:
| Selection | Fractional | Decimal |
| Team A to win | 4/5 | 1.80 |
| Team B to win | Evens | 2.00 |
| Team C to win | 6/4 | 2.50 |
| Team D to win | 2/1 | 3.00 |
Multiply the decimals: 1.80 × 2.00 × 2.50 × 3.00 = 27.00. Return: £5 × 27.00 = £135, a profit of £130.
Another way to see it: £5 at 4/5 returns £9; £9 at evens returns £18; £18 at 6/4 returns £45; £45 at 2/1 returns £135. Each leg’s return is re-staked on the next. That is what “accumulate” means here.
Why the odds look so big
Four selections at prices between 4/5 and 2/1 produced combined odds of 26/1. Eight selections at similar prices would produce combined odds in the hundreds. The size is real, but so is the reason for it: the probability of every leg coming in is the product of each leg’s probability. If each of four teams has a 50% chance, the chance of all four winning is 0.5 × 0.5 × 0.5 × 0.5 = 6.25%, or roughly 15/1 against.
The margin compounds
This is the part that promotional material leaves out. Every price a bookmaker offers contains a margin, typically 5% to 10% on a football match result. On a single, you pay that margin once. On an accumulator, it is built into every leg and multiplies through.
If each of four legs is priced with a 6% margin, the fair combined odds are reduced by roughly 1.06 × 1.06 × 1.06 × 1.06, which is about 26%. On an eight-fold the same margin compounds to around 60%. The bookmaker is not doing anything untoward; it is arithmetic. But it does mean that, pound for pound, an acca is a worse-value bet than the same selections as singles, and the gap grows with every leg. This is also why bookmakers promote accas so heavily and offer “acca insurance” and boosts on them.
Void selections
If a selection cannot be settled, for example a postponed match or a non-runner in a race, that leg is normally treated as void and the bet reduces by one leg. A five-fold with one void leg becomes a four-fold on the remaining selections, with the void leg counted at odds of 1.00. Your stake is not returned; it stays in the bet. Check the shop’s rules, because a few markets (such as ante-post racing) treat non-runners as losers rather than voids.
Each-way accumulators
You can place an acca each-way, which creates two accumulators: one on the win parts and one on the place parts, at the shop’s place terms for each race. The stake doubles. The place acca only pays if every selection at least places. The maths and the pitfalls are the same as for a single each-way bet, covered in the each-way guide.
Accas versus full-cover bets
A four-fold pays only if all four win. A Yankee on the same four selections places 11 bets (6 doubles, 4 trebles, the four-fold), so two winners give you a return, and a Lucky 15 adds the 4 singles, so one winner does. The trade-off is cost: a £1 Yankee costs £11 and a £1 Lucky 15 costs £15, against £1 for the four-fold. Full-cover bets are not a way to reduce the bookmaker’s margin, only a way to spread the stake so that partial success returns something. The glossary lists the line counts for each.
Writing an acca in a shop
On the slip, list each selection with its event and time, then write the bet type (“4-fold”, “5-fold acca”) and the stake once. If you want singles or a Lucky 15 as well, write those separately. The till prints a receipt showing each leg, the price you took (or SP), and the total stake. Check the legs before you leave the counter; a wrong team or a missed line cannot be corrected once the first event has started.
Football accas in shops usually settle at the price displayed when you placed the bet. Racing legs can be taken at the board price or SP, leg by leg.
Before you place one
- An acca is entertainment with a small chance of a big return, not a strategy. Treat the stake as spent when you hand the slip in.
- Adding legs makes the potential return grow faster than most people’s intuition about the odds of winning.
- Use the bet calculator to see the return and total stake before betting, especially for each-way or full-cover versions.
- If you find yourself chasing losses with bigger accas, read our responsible gambling page.