WhichBookmakerCalculator · 2026-09-25
Accumulator calculator
Enter the odds for each leg and your stake. You get the combined odds, the return and profit if every leg wins, and the number most acca calculators hide: how much of the bet the bookmaker's margin eats once it is multiplied through every selection.
Decimal (2.0), fractional (evens, 6/4) or American (+150)
19+.
How the margin compounds
The bookmaker's edge on a single bet is its margin. On an accumulator the edge is taken on every leg, so it multiplies. This is the combined margin at the margin per leg you entered, for one to ten legs.
| Legs | Combined margin | Share of a fair return you keep |
|---|---|---|
| 1 | ||
| 2 | ||
| 3 | ||
| 4 | ||
| 5 | ||
| 6 | ||
| 7 | ||
| 8 | ||
| 9 | ||
| 10 |
How the calculator works
An accumulator wins only if every selection wins. The return is stake × leg 1 odds × leg 2 odds × … × leg n odds. Three legs at 2.0 each give combined odds of 8.0, so a £10 stake returns £80.
Every leg's price includes the bookmaker's margin. If the fair chance of a leg is p, the bookmaker prices it as if the chance were p × (1 + m). Across n legs the overpricing multiplies: the combined margin is (1 + m)ⁿ − 1. Five legs at 5% is 27.6%, not 25%, and it is charged on the whole stake.
The "fair return" row shows what the same accumulator would pay if every leg were priced with no margin, so you can see the gap. The share you keep is 1 ÷ (1 + m)ⁿ: at 5% per leg a five-fold keeps 78% of its fair value, a ten-fold 61%.
What this means for how you bet accas
- Fewer legs, fewer margins. Every leg you add multiplies the bookmaker's edge as well as your potential return.
- Low-margin bookmakers matter more on accas than on singles: 3% per leg on a five-fold is 16%, 6% per leg is 34%.
- Acca insurance and acca boosts are marketed because accumulators are the most profitable product a bookmaker sells; a boost of 10% rarely covers the extra margin of the legs it requires.
- Do not add a short-priced leg "for value": a 1.10 leg adds almost nothing to the return and still carries a full margin.
Link to this calculator
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https://whichbookmaker.io/ca/accumulator-calculator<a href="https://whichbookmaker.io/ca/accumulator-calculator">Accumulator calculator — WhichBookmaker</a>Text and method: CC BY 4.0. Attribute to WhichBookmaker with a link.
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Frequently asked questions
How do you work out accumulator odds?
Multiply the decimal odds of every leg together. Three selections at 1.5, 2.0 and 3.0 give combined odds of 1.5 × 2.0 × 3.0 = 9.0. Multiply by the stake for the return: £10 returns £90, a profit of £80. Fractional odds must be converted to decimal first (add 1 to the fraction: 6/4 becomes 2.5).
Why does the bookmaker's margin matter more on an accumulator?
Because it is applied to every leg and the legs multiply. A 5% margin on a single is a 5% edge; on a four-fold it is (1.05)⁴ − 1 = 21.6%, on a ten-fold 62.9%. A ten-leg accumulator at a typical bookmaker pays roughly 61% of what a fair price would.
What happens if one leg is a non-runner or void?
That leg is settled at odds of 1.0 and removed, so a five-fold becomes a four-fold at the remaining odds. The bet is not lost. Postponed matches are usually voided in the same way if not played within the bookmaker's stated window.
Is acca insurance worth it?
Sometimes, if it comes without extra conditions. Acca insurance refunds the stake (usually as a free bet, not cash) when exactly one leg loses, and typically requires five or more legs at minimum odds. The extra legs add more margin than the insurance gives back in most cases; use the calculator to compare the combined margin of the qualifying bet against the value of a free-bet refund.