A worked example
With five independent legs and an assumed 5% overround on every market, the model returns 100 × (1 / 1.05)^5 = 78.35 per 100 staked. That is an effective expected loss of 21.65%, not simply 5 × 5%. This is a mathematical example, not a forecast for a particular ticket.
How the calculation works
The model assumes proportional pricing with the same overround m on each leg. The expected return multiplier is (1 / (1 + m / 100))^n, where n is the number of legs. The effective expected loss is 1 minus this multiplier. The input is market overround, not a bookmaker’s measured profit or your own estimated edge.
What this result does not tell you
The model assumes independent selections, equal overround and no pricing advantage. Correlated selections, different margins, boosts, taxes, commission and settlement rules can change the result. Expected return is an average over repeated trials under the assumptions; it does not predict whether one accumulator will win.
Common questions
Does a five-leg ticket always lose 21.65%?
No. The example describes an expectation under stated assumptions. An individual ticket can win or lose its stake.
Does this calculate the payout of my ticket?
No. It estimates the cumulative cost of the assumed overround. The quoted combined odds determine a winning ticket’s payout.
Why is one leg at 5% overround not a 5% expected loss?
Under proportional pricing, the return is 1 / 1.05, so the expected loss is about 4.76%. Overround and expected loss are different quantities.
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