Accumulator calculator
Add your legs and see the combined price, what a stake returns, and how likely the whole thing is to land. Then look at the last figure, which is the one the accumulator promotions never show you.
Why the margin compounds
Each leg is already priced below its fair value — that shortfall is the bookmaker's
margin. Multiplying the legs together multiplies the shortfalls too, so an
accumulator's total margin is 1 − (1 − m)n, not
m. Four legs at 5% each cost over 18%; eight legs cost about 34%.
- This is why accumulators are promoted so hard. They are the highest-margin product on the book, which is also why they carry the free bets and the "acca insurance".
- The big return is doing the work on you, not for you. A large potential payout attached to a small probability is the same trade a lottery ticket offers.
- Correlated legs break the arithmetic. If two selections depend on the same event, the combined probability is not the product of the two — and bookmakers price related contingencies separately for exactly that reason.