Term
Expected ValueEV
The average outcome of a bet if you placed it infinite times.
Definition
Expected Value (EV) is the average amount a bet pays out over an infinite repetition of identical conditions. Calculated as (probability of win × profit if won) − (probability of loss × stake). Bets with positive EV (+EV) are mathematically profitable in the long run; -EV bets bleed bankroll regardless of short-term variance.
Example
Stake $100 on +120 odds (profits $120 on win) with a modelled 50% win probability. EV = (0.50 × 120) − (0.50 × 100) = +$10. Repeat infinitely, you make $10 per bet on average.
Why it matters
EV is the bridge between edge and bankroll growth. Every Bettor Score-passing bet should be +EV before sizing. Variance turns +EV bets into short-term losses, which is why drawdown rules exist.
Related terms
Edge
The percentage difference between your estimated probability of an outcome and the sportsbook’s implied probability from the offered odds.
Kelly Criterion
A formula that prescribes the bet size which maximises logarithmic bankroll growth given a quantified edge and odds.
Variance
The dispersion of bet outcomes around their expected value — high variance means results swing wildly even when long-run +EV holds.
Return on InvestmentROI
Cumulative profit (or loss) expressed as a percentage of total amount staked across all settled bets.
Last updated ·