Math & measurement
Expected value (EV)
The average profit or loss a bet would produce if repeated many times: (win probability × profit) − (loss probability × stake). A bet is +EV when the odds pay more than the true probability justifies — decimal odds × true probability greater than 1 — and long-term profit is simply accumulated +EV.
The practical difficulty is that nobody hands you the true probability. The standard estimate is the de-vigged market consensus: strip the margin from many books' prices and compare the best available price against that fair baseline.
Go deeper: EV calculator →
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