Accumulator Bet Explained: How Doubles, Trebles and Accas Pay

An accumulator bet links horses in different races into one bet. The stake goes on the first horse; if it wins, the whole return is staked on the second; if that wins too, the new total goes on the third, and so on. Two horses make a double, three a treble, and four or more an accumulator, often shortened to an acca.

Every leg has to win. One loser, anywhere in the chain, and the bet is gone. That single rule is the whole story of accumulators, and everything else on this page follows from it.

The double bet and the treble bet

A double bet is the smallest accumulator. £5 on a double at 6/4 and 7/4 works like this: if the 6/4 horse wins, the £5 has become £12.50. That £12.50 then rides on the 7/4 horse, and if it wins too, the return is £12.50 × 2.75, which is £34.38.

You can get there in one step by multiplying the decimal odds: £5 × 2.5 × 2.75 gives the same £34.38. The order of the races doesn’t matter to the maths at all, only that both horses win.

A treble bet adds a third leg. Put an 11/10 horse on top of the same double and the £5 treble returns £5 × 2.5 × 2.75 × 2.1, which is £72.19. Three winners at modest prices have turned £5 into more than fourteen times the stake. The calculator at the foot of this page is loaded with that treble.

Compare that with three £5 win singles on the same horses, £15 in total. If all three win, the singles return £36.75. The treble returns nearly twice as much from a third of the stake. If one horse loses, though, the singles still return two winners’ worth and the treble returns nothing. That trade is the whole choice.

How an accumulator bet grows

Each extra leg multiplies the price again, which is why accumulators can reach large figures from small stakes. A £2 four-fold at evens, 4/5, 6/4 and 2/1 returns £54. A £1 five-fold with every horse at 2/1 returns £243, and a £1 six-fold with every leg at 6/4 returns £244.14.

The price is real, and so is the chance behind it. On the market’s own view, the three horses in the treble above have implied chances of about 40%, 36% and 48%. Multiply those together and the chance of all three winning is about 6.9%. The treble’s decimal price of 14.44 implies exactly that same figure, which isn’t a coincidence: an accumulator’s price is only the product of its legs’ prices, and so is its chance.

What it does add is margin. Every leg carries the bookmaker’s margin, and in an accumulator those margins multiply along with the odds. A long accumulator is therefore a bet on a very unlikely event at a price that has been shaded in the bookmaker’s favour several times over. That doesn’t make it a bad bet for a small stake. It makes it a bet to place knowing what it is.

How long should an accumulator bet be?

There is no correct length, but the arithmetic shows how quickly the chance falls away. Give every leg the same implied chance and multiply.

Three horses at 6/4, each about a 40% chance on the market’s figures, make a treble with roughly a 6.4% chance of landing: about one in sixteen. Six horses at 6/4 make a six-fold with about a 0.4% chance: roughly one in 244, which is exactly what its price of 244.14 says. Each extra leg at 6/4 divides the chance by two and a half.

That is the honest shape of an accumulator. Short ones, a double or a treble on horses you rate highly, land often enough to be a real bet. Long ones are closer to a lottery ticket: cheap to buy, occasionally spectacular, and expected to lose. Neither is wrong. They are simply different bets, and a six-fold staked as though it were a double is where accumulator betting goes wrong.

A practical middle ground, if you have six horses you like, is to split them: two trebles, or three doubles, rather than one six-fold. You give up the huge figure at the top in return for a much better chance that something pays.

Each way accumulators

An each way accumulator is two accumulators on the same horses: one to win and one to place. £5 each way on a treble costs £10.

The place accumulator is settled at each horse’s place price, and every horse has to be placed. A winner counts as placed. Using the treble horses at 1/5 terms, if all three are placed without any of them winning, the place treble returns £10.71, just over the £10 stake. If all three win, the win treble returns £72.19 and the place treble adds £10.71, £82.89 in total.

On a double, each way can rescue part of a near miss. Take £5 each way on the 6/4 and 7/4 horses, both in races paying 1/4. If the 7/4 horse wins and the 6/4 horse only places, the win double loses, and the place double returns £9.88 from the £10 staked. Almost the stake back, on a day the straight double would have lost it all. The each way guide explains how the terms are set race by race.

Non-runners, Rule 4 and dead heats

A non-runner doesn’t sink an accumulator. That leg is removed and the rest carries on, so a four-fold becomes a treble, and a double becomes a single. In the £2 four-fold above, if the 4/5 horse is withdrawn and the others win, the bet is settled as a treble on evens, 6/4 and 2/1 and returns £30 instead of £54.

Rule 4 cuts the price of one leg, and because everything multiplies, the cut carries through the whole bet. In the £5 treble, a 25p deduction on the 6/4 leg brings that price down to 2.125 in decimals, and the treble returns £61.36 instead of £72.19. The Rule 4 page has the deductions.

A dead heat on one leg divides the stake at that point, and the reduced amount rides on. If the 6/4 horse in the treble dead heats for first with one other, half the stake is carried forward at 6/4, and the treble returns £36.09, exactly half of the full return.

Doubles only, trebles only and full cover

An accumulator puts everything on one outcome. The step in between is to back every double, or every treble, from a group of horses, without the bigger multiples.

With four horses you can choose “doubles”, which is all six pairs, or “trebles”, which is all four groups of three. With four winners at 6/4, 7/4, 11/10 and 2/1, £1 doubles return £39.95 from £6, and £1 trebles return £68.14 from £4. With one loser, the doubles still have three winning pairs and the trebles one winning group.

Going one step further brings you to the full-cover bets, which back every combination at once. The Trixie is the doubles and treble on three horses, the Yankee every multiple on four, and the Heinz every multiple on six. They cost more than a single accumulator on the same horses, and they pay on days when one or two legs fail. The accumulator bet is the cheapest and the most fragile member of the family.

Settling an accumulator by hand

An accumulator is the easiest multiple to settle, because there is only one line. Turn every price into decimals, multiply them together and multiply by the stake. If any leg lost, the answer is nothing.

For a non-runner, leave that leg out, or count it as 1.0, which comes to the same thing. For a Rule 4 deduction, reduce that horse’s winnings first: at 6/4 with a 25p deduction, the winnings of 1.5 become 1.125, so the decimal is 2.125. For a dead heat, divide that leg’s decimal by the number of horses tied. Then multiply as usual.

The one check always worth making on a settled accumulator is the price used for each leg. A price you took stands. A leg left to SP is paid at the starting price, and it is easy to assume a morning price when the slip said SP.

Placing an accumulator

The rule on the slip is that every leg must be a separate race, and the order you write them in doesn’t change the settlement. In a betting shop, list the horses with their meetings and race times, write “four-fold” or “acca” as the bet, and give the stake. Online, adding several selections to a bet slip offers the accumulator among the multiples.

Some firms offer extras on accumulators, such as a refund if one leg loses, or a percentage bonus on the winnings for longer accumulators. They vary from firm to firm, and the terms decide what they are really worth. The bet calculator settles the bet on its own terms, with every leg, each way, non-runners, Rule 4 and dead heats, and it is worth running a planned accumulator through it once, with one leg set to lose, just to see the number that matters most.

There is a quiet appeal to an accumulator bet that the arithmetic doesn’t capture: it keeps an afternoon of racing interesting to the last leg, and every winner along the way raises the stakes on the next race. That is a perfectly good reason to place a small one. It is a poor reason to place a large one.