Acca Odds Calculator Explained: How Accumulator Odds Work

Accumulator odds are the odds of every leg multiplied together. A four-leg acca at 1.50, 1.80, 2.10 and 1.60 pays 1.50 × 1.80 × 2.10 × 1.60 = 9.07 in decimal odds, so a £10 stake returns £90.72 if every leg wins. That is all a standard acca calculator does, and you can do it with a phone calculator in ten seconds, or by using our acca calculator.

This guide shows the calculation, the fractional-odds shortcut, what happens when a leg is void, and the part calculators usually leave out: your real chance of winning.

The basic formula#

Use decimal odds. They already include your stake, which makes multiplying straightforward.

Total return = stake × odds of leg 1 × odds of leg 2 × odds of leg 3 × ... Profit = total return minus stake

Worked example with a £10 stake on a three-leg acca:

Combined odds: 5.67. Total return: £56.70. Profit: £46.70.

Fractional odds work the same way#

UK bookmakers often show odds as fractions. Convert each one to decimal first: divide the top by the bottom and add 1.

The three-leg acca above at 1/2, 4/5 and 11/10 gives the same 5.67. Some bookmakers round fractional prices to the nearest available fraction, so a slightly different total on a betting slip is normal.

From odds to probability#

Decimal odds convert to an implied probability with one step: 1 ÷ odds.

• 1.50 implies 66.7%
• 1.80 implies 55.6%
• 2.10 implies 47.6%

For the whole acca, 1 ÷ 5.67 = 17.6%. This is the chance the bookmaker's price implies. It is not the same as the true chance, because the price includes the bookmaker's margin. For how to strip that out, read how to read implied probability and remove the margin.

Why probabilities shrink faster than odds grow#

When you add a leg, odds multiply and probabilities multiply. Because each probability is below 1, the combined chance falls quickly.

A six-leg acca made of 70% selections wins roughly once in every 8.5 attempts. Fair odds would be 8.50. The price you are actually offered is lower, which is the subject of the next section. For a longer look at this, see how many legs an acca should have.

Where the bookmaker margin hides#

Suppose a bookmaker prices each of those 70% legs with a 5% margin built in. Each leg's implied probability becomes 73.5%, so the odds are 1 ÷ 0.735 = 1.36 rather than 1.43. Over six legs the combined odds are 1.36 to the power of 6, which is 6.34, not 8.50.

You still win 11.8% of the time, but you are paid at 6.34 instead of 8.50. Expected return per £1 staked: 0.1176 × 6.34 = £0.746. The margin took about 25p in the pound. The full breakdown is in the hidden cost of accumulators.

Voided legs, cash out and boosts#

Voids. If a match is postponed or abandoned, most bookmakers settle that leg at 1.00. A void in the three-leg example above leaves 1.50 × 2.10 = 3.15, so £10 returns £31.50 if the other two win. Check the abandonment rules of your bookmaker, because the time limit differs.

Cash out. Cash out offers are priced by the bookmaker. They include margin as well, so a cash out is usually a little below the fair value of what remains. Cashing out is not wrong, but it is not free.

Boosts. Percentage acca boosts add to the winnings. They can offset part of the compounded margin, with caps and conditions. See acca insurance and boost offers explained.

Full-cover bets from the same selections#

An acca is one bet. Bookmakers also offer bets that split the same selections into several smaller accumulators so that one loser does not wipe everything out.

Your total stake is the unit stake times the number of bets. A £1 Lucky 15 costs £15. Full-cover bets lower the chance of a total wipe-out, but each part still carries margin, and a single winner usually pays less than your total stake.

A quick manual checklist#

1. Convert every leg to decimal.
2. Multiply to get the combined odds.
3. Multiply by stake for the total return.
4. Take 1 ÷ combined odds for the implied chance.
5. Multiply your own leg probabilities for the real chance.
6. Compare 4 and 5. If 5 is lower, the bet has negative expected value.

If you want the legs and the maths done together, the ArtificialAcca generator shows each leg's odds, de-vigged probability and the reasoning behind it. You can also see how every daily acca settled on the results page.

A worked slip with fractional prices#

Here is a five-leg slip priced in fractions, staked at £5.

Combined odds are 25.85 in decimal, or about 24.85/1. A £5 stake returns £129.24 for a profit of £124.24. The implied probability is 1 ÷ 25.85 = 3.9%, so the bookmaker's price says the bet should land roughly once in 26 attempts, and that already includes the margin.

Compare that with your own estimate. If you think the legs are 70%, 60%, 55%, 45% and 40%, the combined chance is 0.70 × 0.60 × 0.55 × 0.45 × 0.40 = 4.2%. That is slightly above the implied 3.9%, but on estimates this rough, the difference is well inside the error. It is a reminder that a long price can look like value when it is really noise.

Things that change what you are paid#

The arithmetic above gives the headline payout. Several practical details can change it.

• Maximum payout limits. Many bookmakers cap the total winnings on a single bet. A long acca with a big combined price can hit the cap, which makes the stated odds partly academic.
• Displayed prices are rounded. Decimal odds are shown to two decimal places, so multiplying the displayed prices can differ slightly from the figure on your slip, especially over many legs.
• The price when you bet is the price you get. For fixed-odds football bets, the odds at the moment you confirm are the odds you are paid at, even if they move afterwards.
• Odds boosts and offers. A boosted acca replaces the standard price, so calculate with the boosted figure.

If a total on your slip looks wrong, check the legs one at a time. A single leg with a different price than you expected, or a market that does not qualify for a boost, is the usual cause.

18+ only. Accumulators lose more often than they win, and the numbers above are probabilities, not promises. Gamble with money you can afford to lose. For free, confidential support visit BeGambleAware.org or call 0808 8020 133.