Direct Answer
An expected-value calculation converts a probability estimate and a price into a per-bet expected return. EV = (probability of win × profit) − (probability of loss × stake). Positive EV bets win money on average; negative EV bets lose money on average.
Key Takeaways
- EV = (p_win × profit) − (p_loss × stake).
- Positive EV wins money on average over many trials.
- EV quality depends entirely on probability quality.
Worked example
$100 at +120 on a 50% outcome: EV = (0.50 × $120) − (0.50 × $100) = $10. Per-bet expected return = +10%. Over 1,000 such bets, expected profit ≈ $10,000 against $100,000 staked.
Where the probability comes from
It comes from a model, a market read, or a de-vigged price from a sharper book. The quality of the EV estimate is entirely a function of the quality of the probability estimate. Garbage probability in, garbage EV out.
Frequently asked questions
Can I trust EV from my own model?+
Only if your model has been validated against closing line value. Otherwise EV is wishful thinking.
Educational only. Not wagering, financial, or legal advice. See our editorial policy.