What happens to an acca if one leg is void?

The void leg is usually removed and the acca is settled on the remaining legs, as if that leg had odds of 1.00. A four-fold with one void becomes a treble.

How are accumulator odds calculated?

Multiply the decimal odds of every leg. 2.00 × 1.80 × 1.50 = 5.40, so a £10 acca returns £54 if all three win.

What is a double, treble and four-fold?

A double has two legs, a treble three and a four-fold four. Any bet with two or more legs is an accumulator.

Are accumulators good value?

Not inherently. Each leg carries the bookmaker's margin, and those margins compound across the legs. The odds look big because the chance of every leg winning is small.

What is an accumulator (Acca) bet?

By ProbaPredict Data Desk · Last reviewed Sat, 3 Oct 2026

An accumulator, or acca, is a single bet that combines two or more selections, called legs. Every leg must win for the bet to pay. The odds multiply together, so returns grow quickly, but so does the chance of losing: four legs at 60% each win together only about 13% of the time.

How does an accumulator work?

You pick several outcomes, for example three home wins and an Over 2.5 goals, and combine them into one bet. The stake rides on all of them together. If every leg wins, you are paid at the combined odds; if any single leg loses, the whole bet loses. A two-leg acca is a double, three is a treble, four is a four-fold, and so on.

How are acca odds calculated?

Multiply the decimal odds of every leg. With fractional odds, convert each to decimal first: 5/4 = 2.25, 10/11 = 1.9091, 6/4 = 2.50, 2/1 = 3.00. Their product is 2.25 × 1.9091 × 2.50 × 3.00 = 32.22, so a £10 four-fold returns £322.16 if every leg wins. Our acca calculator does this in any format and handles void legs.

Why does the chance of winning fall so fast?

Probabilities multiply too. If each leg has a 60% chance, two legs win together 36% of the time, three legs 21.6%, four legs 13.0% and six legs 4.7%. Each extra leg adds a new way to lose. That's the reason acca odds look generous: they are paying for a low chance, not offering a bargain.

How does the margin add up?

Every leg carries the bookmaker's margin. In the closing odds we hold, the average 1X2 margin is 5.3% per match. Across four legs the combined overround is roughly (1 + 0.053)⁴ − 1 = 22.9%, before considering any extra margin bookmakers add to individual prices.

Average bookmaker margin in closing odds, by league

League	Matches	1X2 margin	Over/Under 2.5 margin
Premier League	1,950	4.4%	4.9%
Bundesliga	1,566	4.8%	5.2%
La Liga	1,969	4.8%	5.2%
Serie A	1,950	4.9%	5.2%
Ligue 1	1,723	5.0%	5.3%
Championship	2,855	5.5%	5.6%
Eredivisie	1,593	5.7%	6.1%
Primeira Liga	1,592	6.2%	6.0%
Brasileirão Série A	2,177	6.3%	not in source

Source: ProbaPredict analysis of 17,375 matches, updated Sat, 3 Oct 2026. Market-average closing odds from football-data.co.uk. Margin = sum of implied probabilities − 100%.

Worked example: a four-fold

Our model gives four outcomes: 62%, 55%, 48% and 70%. Combined chance of all four = 0.62 × 0.55 × 0.48 × 0.70 = 11.5%. Fair combined odds = 100 ÷ 11.5 = 8.70. If a bookmaker's legs multiply to 7.90, its acca implies 12.7%, more than our 11.5%. You would lose this bet nearly nine times in ten even at a fair price.

What happens with void legs?

If a match is postponed or a leg is otherwise void, most bookmakers treat it as odds of 1.00: the acca continues on the remaining legs at lower combined odds. Our acca calculator lets you set any leg to Void to see the new return.

How do our accumulator tips work?

Each day we build ready-made tickets from our highest-probability outcomes and publish them on accumulator tips today. Each ticket shows every leg's probability, the combined chance and fair odds. Tickets are frozen at the first kick-off and graded in public on our accuracy page, including the ones that lose.

Legs from the same match

Combining, say, a home win and Over 2.5 from the same match is not independent: one makes the other more likely. Bookmakers usually price these as "bet builders" with lower combined odds than simple multiplication would give.

UK and US terminology

UK and Ireland: "accumulator", "acca", "double", "treble", "four-fold". US and Canada: "parlay", with legs often in American odds. See what a parlay is.

Common mistakes with accumulators

Adding "safe" legs. A leg at 85% still cuts the chance of the whole ticket by 15%.
Judging by the potential return. Big returns reflect small chances.
Forgetting margins compound. More legs, more margin.
Chasing a near-miss. "Three out of four" pays nothing; don't increase stakes to win it back.

What is a system bet?

System bets such as Trixies, Yankees and Lucky 15s are bundles of doubles, trebles and accumulators covering the same selections, so one losing leg doesn't sink everything. They cost several stakes at once: a Yankee on four selections is 11 bets. The maths of each component bet is unchanged, and the margins still compound, so a system bet is a way of spreading stake, not of improving the odds.

How should you think about acca returns over time?

Because every leg includes a margin and the margins compound, the expected return of an accumulator is usually lower than that of the same legs bet as singles. The occasional big win is memorable, but it is paid for by the many tickets that fall one leg short. Over a long run, most acca bettors get back noticeably less than they stake.

If you enjoy accas as entertainment, a fixed small budget keeps the cost under control. Our accumulator pages show the combined probability and fair odds for every ticket precisely so the chance of winning is visible, not hidden behind the potential return. We grade every ticket in public, including the losers.

Frequently asked questions

What happens to an acca if one leg is void?: The void leg is usually removed and the acca is settled on the remaining legs, as if that leg had odds of 1.00. A four-fold with one void becomes a treble.
How are accumulator odds calculated?: Multiply the decimal odds of every leg. 2.00 × 1.80 × 1.50 = 5.40, so a £10 acca returns £54 if all three win.
What is a double, treble and four-fold?: A double has two legs, a treble three and a four-fold four. Any bet with two or more legs is an accumulator.
Are accumulators good value?: Not inherently. Each leg carries the bookmaker's margin, and those margins compound across the legs. The odds look big because the chance of every leg winning is small.

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