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Expected value (EV)

Expected value is what a bet makes on average if placed many times: stake × (probability × decimal odds − 1). A positive EV means the odds beat the chance.

Example

A bet of 10 at 2.75 on a 40% chance has an EV of 10 × (0.40 × 2.75 − 1) = +1.00, an edge of 10%.

Go further

Expected value in betting, in plain numbersThe full explainer, on the blogExpected value calculatorWhat a bet makes on average, its edge, and the swing over many bets.

Related terms

Edge (value bet)A bet has a positive edge when your probability times the decimal odds is over 1: the price pays more than the chance deserves. The edge is that, minus 1.VarianceVariance is how far real results stray from what the odds and the chances predict. In betting it is large: good bets can lose for weeks before the edge shows.Kelly criterionThe Kelly criterion stakes the share of a bankroll that maximises its long-run growth: the edge divided by the net odds. With no edge, it stakes nothing.