Expected Value (EV) Calculator
Enter your estimated probability that a bet wins and the American odds the sportsbook is offering. The calculator returns expected value per $1 staked, edge percentage, and Kelly Criterion stake recommendation.
Adjust the inputs above to see live EV calculation.
How to use this calculator
Expected value tells you whether a bet is worth taking on average. If EV is positive, the bet wins money over many trials; if negative, it loses. The Kelly Criterion stake recommendation is the mathematically optimal amount to risk given your edge.
Example: NFL game where you estimate Team A has a 55% probability of winning. The sportsbook offers -110 (52.4% implied). Your edge: 2.6 percentage points. EV per $100 stake: roughly $5.20. Kelly recommends ~5% of bankroll; half-Kelly is the safer recommendation.
For credible probability estimates, you need to track closing line value over 200+ bets to verify your edge is real. See also our value betting guide.
Frequently Asked Questions About EV
What is expected value (EV) in sports betting?
Expected value is the average profit (or loss) per dollar wagered if you placed the same bet many times. Positive EV means the bet wins money on average; negative EV means it loses money on average. The formula: EV = (probability of win × payout) − ((1 − probability of win) × stake).
What does +EV mean in sports betting?
+EV ("positive expected value") means the bet wins money on average over many trials. To find +EV bets you need a probability estimate that exceeds the implied probability of the offered odds. Sustained +EV betting is what separates winning bettors from losing ones.
How accurate does my probability estimate need to be?
You need to consistently beat the closing line value (CLV). If your estimates produce average +1% CLV or better over 200+ bets, your edge is real. See our /guides/closing-line-value/ for the full methodology.
How do I use EV to size bets?
Combine EV with the Kelly Criterion: optimal stake fraction = edge / (decimal odds − 1). Larger edge = larger stake. Most pros use half-Kelly or quarter-Kelly to dampen variance. See our /tools/kelly/ calculator for stake sizing.
Can a +EV bet still lose?
Yes — frequently in the short term. EV is a long-run concept. A +5% EV bet at -110 still loses 47% of the time per individual bet. Profitability emerges over 500-1,000+ bets, not over 10. Variance dominates short samples.