By the OpenBookies team · Updated July 2026 · 9 min read
An accumulator — the acca — is one bet that combines several selections, where every single leg must win for the bet to pay out. The winnings from each leg roll onto the next, so the odds multiply and small stakes can produce big returns. That multiplication is also the catch: one losing leg and the whole bet is gone. This guide covers the maths with worked examples, what happens when a leg is void, why bookmakers promote accas so heavily, and how to place one over the counter in a betting shop.
What counts as an accumulator?
Strictly, an accumulator is four or more selections in one bet. Two selections make a double, three make a treble, and from four upwards the bet takes the name of its size — a four-fold, five-fold and so on. In everyday use "acca" covers the lot: if the legs multiply and they all have to win, it's an acca. The selections must be independent — you can't combine the same horse to win and to place, or two outcomes from the same match, in one accumulator.
| Name | Selections |
|---|---|
| Double | 2 |
| Treble | 3 |
| Four-fold (acca) | 4 |
| Five-fold | 5 |
| Six-fold | 6 |
| Seven-fold | 7 |
| Eight-fold | 8 |
If you're not yet comfortable with singles, doubles and the rest of the menu, start with our types of bets guide — an acca is just those building blocks stacked on top of each other.
The maths: how acca odds multiply
The cleanest way to price an accumulator is with decimal odds, because the calculation is one line: multiply your stake by the decimal odds of every leg. If you think in fractions, convert each price first — the decimal is the fraction plus one, so 6/4 becomes 2.50 (see betting odds explained for the full conversion table).
Here's a £10 four-fold, showing the running return after each leg wins. Notice how the entire return from one leg — stake and profit — becomes the stake for the next:
| Leg | Fractional odds | Decimal odds | Running return |
|---|---|---|---|
| Leg 1 | 1/1 (evens) | 2.00 | £20.00 |
| Leg 2 | 6/4 | 2.50 | £50.00 |
| Leg 3 | 1/2 | 1.50 | £75.00 |
| Leg 4 | 2/1 | 3.00 | £225.00 |
In one line: £10 × 2.00 × 2.50 × 1.50 × 3.00 = £225 — £215 profit from a £10 stake. The same £10 spread as four £2.50 win singles at those prices would return at most £22.50 if every one of them won. That contrast is the whole appeal of the acca: the upside is dramatically bigger, in exchange for a dramatically smaller chance of collecting anything at all.
Roughly how likely is an acca to win?
Multiply the implied probabilities. Four legs that are each about a 60% chance combine to 0.6 × 0.6 × 0.6 × 0.6 ≈ 13% — and that's a deliberately conservative acca of short-priced favourites. A typical Saturday five-fold of evens shots has roughly a 3% chance of landing. Big acca payouts make the news precisely because they're rare.
Non-runners, void legs and postponed matches
A leg that never takes part — a non-runner in a horse race, a postponed or abandoned football match under most house rules — is treated as void, not as a loser. The leg simply drops out and the bet stands on what's left: your five-fold becomes a four-fold, your double becomes a single. The potential return shrinks, but the bet survives.
One wrinkle from horse racing: if you took an early price and a significant horse is withdrawn from that race, a Rule 4 deduction can reduce the odds on your remaining selection in that race — the standard industry adjustment for the race becoming easier to win. Bets struck at starting price (SP) after withdrawals already reflect the reduced field.
Why bookmakers love accas
Every price a bookmaker offers contains a margin — the overround. On a single bet you pay that margin once. On an accumulator you pay it on every leg, multiplied together. If each leg carries a typical 5% margin, a treble carries roughly 16% combined, a five-fold about 23%, and an eight-fold over 30%. The bigger the acca, the larger the bookmaker's mathematical edge — which is exactly why acca promotions, boosts and insurance offers are so heavily advertised.
That doesn't make accas a mug's bet — a small stake for a big potential return is a perfectly reasonable bit of fun, and it's how most newsworthy wins happen. It does mean an acca is an entertainment bet, not a value bet: keep stakes small, and treat anything it returns as a bonus.
Placing an acca in a betting shop
Accumulators are a betting shop staple, especially on Saturday football. Two ways to do it:
On a football coupon
Grab a coupon from the rack, mark your selections, write your stake and the bet type (e.g. "£5 five-fold") and hand it over. The till prices the multiple automatically and your printed slip shows every leg and the total odds. Check the slip before you leave the counter — once you've walked away it's much harder to correct a mistake.
On a blank slip
For racing or mixed-sport accas, write each selection on one slip — time, meeting and horse for racing legs — plus the stake and "four-fold" (or whatever the size is). If you want the current board prices rather than SP, ask the cashier to "take the price" on each leg. New to the counter? Our guide to how betting shops work walks through the whole process, and you can find your nearest shop with our betting shop map.
Five common acca pitfalls
1. Adding legs for the sake of it. Every extra leg multiplies the risk and the bookmaker's margin. A short-priced "banker" added to round the odds up rarely improves the bet.
2. Related contingencies. You can't combine outcomes that affect each other — a team to win and the same team to win 2–0, say. Tills and apps will reject them or reprice them as a different bet.
3. Confusing an acca with a full-cover bet. A Yankee or Lucky 15 on four selections costs 11 or 15 times the unit stake because it contains many bets; a four-fold is one bet at one stake. Know which one you're writing on the slip.
4. Forgetting each-way doubles the cost. An each-way acca is two accumulators — one win, one place — so £5 each-way costs £10, and the place acca settles at the place terms of every leg. See each-way betting explained for how those terms work.
5. Chasing losses with bigger accas. The maths only gets worse as the legs stack up. Set a stake you're happy to lose and stick to it — and if betting stops being fun, free and confidential help is available from GambleAware.