Free tool
Expected Value (EV) Calculator
Check whether a bet has positive expected value before you place it.
Expected value (EV) is the average profit or loss you would make if you placed the same bet many times. A positive EV means the bet is profitable in the long run; a negative EV means it loses. Enter the odds, your estimate of the true win probability and a stake to see the EV.
Your bet
Expected value
- EV
- 0.50
- EV %
- 5.00%
How it works
Expected Value (EV) estimates the average profit or loss a bet would produce if it were repeated many times under the same conditions. From the decimal odds, your estimated win probability and your stake, the calculator returns the expected profit or loss per bet. The formula is EV = (p × (odds − 1) × stake) − ((1 − p) × stake), where p is your probability of winning. The first term is your expected gain when the bet wins; the second is your expected loss when it loses. A positive EV means the bet is profitable in the long run; a negative EV means it loses money over time. EV is the foundation of value betting. Rather than asking whether a single bet will win, it asks whether the price on offer is generous relative to the true chance of the outcome. Placing positive-EV bets consistently is what separates disciplined bettors from those who simply chase results.
Worked example
Suppose the decimal odds are 2.50, you estimate the probability of winning at 0.45, and you stake £10. Expected gain if it wins = p × (odds - 1) × stake = 0.45 x 1.50 x 10 = £6.75 Expected loss if it loses = (1 - p) × stake = 0.55 x 10 = £5.50 EV = £6.75 - £5.50 = +£1.25 The positive result means that, on average, this bet returns £1.25 in profit each time it is placed under these conditions, marking it as a long-term-profitable, positive-EV bet.
EV is only as reliable as the win probability you supply; an inflated estimate can make a losing bet look profitable. A single result tells you nothing, so judge EV across hundreds of bets rather than reading anything into one outcome.
Frequently asked questions
What does positive expected value mean?
Positive EV means that, based on your probability estimate, the bet would return a profit on average if it were placed repeatedly. It indicates the odds are longer than the true chance of the outcome warrants, which is the hallmark of a value bet.
How do I estimate the win probability for EV?
You can derive it from your own model, from statistical analysis, or from the implied probability of a sharp, low-margin market. The accuracy of this estimate is critical, because EV is only meaningful if your probability is realistic.
Can a bet have positive EV but still lose?
Absolutely. EV is a long-run average across many repetitions, not a prediction of any single result. Positive-EV bets will lose individually on a regular basis; the edge only emerges over a large sample.
How is EV different from the Kelly criterion?
EV tells you whether a bet is profitable on average and by how much, while Kelly uses that edge to decide how much of your bankroll to stake. EV identifies the value; Kelly sizes the bet that captures it.
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