Accumulator calculator
Add 2 to 12 selections, enter each leg's odds, see combined odds, total return, and the bookmaker's implied probability.
How accumulators work
An accumulator combines multiple selections into a single bet. Every leg has to win for the bet to pay out. Returns are the product of all decimal odds, multiplied by your stake.
Implied probability.The reciprocal of combined odds is the bookmaker's implied chance that the bet lands. A 4-fold at 30.0 has 3.33% implied probability — that's the bookmaker's view, before any margin. Once you account for the typical 5-7% margin built into UK racing prices, your true edge per leg has to be enough to beat that compounded markup.
Worked example. £10 stake on a 4-fold: legs at 2.0, 2.5, 3.0 and 4.0. Combined odds 2.0 × 2.5 × 3.0 × 4.0 = 60.0. Return = £10 × 60.0 = £600. Profit = £590. Implied probability = 1 / 60.0 = 1.67%.
FAQ
- How does an accumulator work?
- An accumulator (often called an acca or parlay) is a single bet on multiple selections where every selection must win for the bet to pay out. Returns are calculated by multiplying all the decimal odds together, then by your stake. If any leg loses, the whole bet loses — no partial returns.
- What are the combined odds on an accumulator?
- Multiply every leg's decimal odds together. Three legs at 2.0, 3.0 and 2.5 give combined odds of 2.0 × 3.0 × 2.5 = 15.0. £10 stake at 15.0 returns £150 (£140 profit). The bookmaker's implied probability is 1 / combined odds = 1 / 15.0 = 6.67%.
- How many selections can an accumulator have?
- Most UK bookmakers allow 2 to 12 selections in a single accumulator (some go higher). Anything above about 8 legs is statistically very unlikely to land, even at short odds — by leg 8 you've usually compounded enough variance that the bookmaker's margin per leg dominates the expected value.
- Is acca insurance worth taking?
- Acca insurance (your stake refunded if one leg lets you down) tightens the price on long-shot accumulators — you're trading variance for a smaller payout. It's worth it on 5+ leg accas where any single defeat is the most likely outcome; less so on 3-4 legs where the win is plausible enough. Always check whether the bookmaker reduces the price elsewhere to fund the insurance.
- Why do accumulators rarely win?
- Each leg includes the bookmaker's margin. Combining N legs compounds N margins — by 5-6 legs you're betting into roughly 25-30% theoretical overround vs. true probability. The longer the accumulator, the worse the value (unless you genuinely have an edge on every leg). The calculator's implied probability number lets you see this in real time.