This calculator is an educational tool for understanding accumulator returns and how multiple selections combine. It does not provide betting advice, tips, or predictions.
Acca Calculator
Calculate combined odds, implied probability, and returns.
Accumulator bets
Build an accumulator by entering each selection’s odds, result and Rule 4 deduction. Totals update live so you can see the
combined return as you tweak the legs.
How the acca calculation works
Accumulator rule: all legs must win for a full return. If any leg is marked Lost, the return is £0.
Void legs: treated as odds 1.0 so they do not change the product.
Rule 4: the winning part of a leg is reduced using 1 + (odds − 1) × (1 − rule4).
Fractional odds: convert to decimal as 1 + (a ÷ b).
Total return:unit stake × combined odds, profit is return minus stake.
Always gamble responsibly. This calculator is for information only and does not guarantee profit.
How many legs can I add?
Select a type from single up to twentyfold. The table will always match that number of legs.
Do I need decimal odds?
No. You can switch between decimal and fractional formats and the calculator will convert as needed.
How does Rule 4 change the return?
Rule 4 trims the winnings portion of that selection before the total is combined. The higher the deduction, the lower the return.
What about each-way accas?
Each-way accas depend on place terms. This calculator keeps the toggle for reference but shows win returns only.
When to use an accumulator calculator
An accumulator (or "acca") combines multiple selections into a single bet. All selections must win for the bet to pay out, but the combined odds — and therefore the potential return — grow with each added leg. This calculator lets you model returns from doubles through to twentyfolds, apply Rule 4 deductions, handle void legs, and see the overall implied probability of your combined selections.
Use this calculator before placing an accumulator to understand the true probability of winning. A four-fold acca where each leg has a 50% chance of winning has only a 6.25% chance of landing (0.5⁴). Many bettors underestimate how quickly the probability drops as legs are added, so checking the combined numbers first helps set realistic expectations.
Detailed worked example
You want to place a £5 four-fold accumulator with these selections:
Leg 1: odds 2.0 (implied probability 50%)
Leg 2: odds 1.8 (implied probability 55.6%)
Leg 3: odds 3.5 (implied probability 28.6%)
Leg 4: odds 2.2 (implied probability 45.5%)
The combined decimal odds are 2.0 × 1.8 × 3.5 × 2.2 = 27.72. Your potential return is £5 × 27.72 = £138.60 for a profit of £133.60. However, the combined implied probability is 50% × 55.6% × 28.6% × 45.5% = 3.61%. This means you have roughly a 1-in-28 chance of winning.
Now suppose Leg 3 is voided (non-runner). The calculator treats voided legs as odds of 1.0, so the revised combined odds become 2.0 × 1.8 × 1.0 × 2.2 = 7.92, and the return drops to £5 × 7.92 = £39.60.
Common mistakes with accumulators
Underestimating the combined probability: Each leg you add dramatically reduces your chance of winning. A ten-fold at even money (2.0 each) has less than a 0.1% chance of landing.
Ignoring Rule 4 deductions: If a runner is withdrawn in horse racing, Rule 4 reduces the odds. Not accounting for this leads to overstated expected returns.
Treating accumulators as strategy: Accumulators offer large potential returns but very low probability. They are a form of entertainment, not a reliable staking strategy. The bookmaker's margin compounds with each leg.
Mixing odds formats: Ensure all odds are in the same format (decimal, fractional, or American). The calculator handles conversions, but mixing them manually leads to errors.
