Expected Value (EV) Calculator
Enter American odds, your true win probability and a stake to see a bet’s expected value in dollars and as a percentage — and whether it’s +EV or −EV. Everything runs in your browser; nothing is stored.
What is expected value?
Expected value (EV) is the average outcome of a bet if you could repeat it endlessly. It compares what you win when the bet lands with what you lose when it doesn’t, weighted by how likely each is. If your estimate of the win probability is higher than the odds imply, the bet is positive EV; if it’s lower, it’s negative EV.
The formula
EV = S × ( p × b − (1 − p) )
EV % = EV ÷ S × 100
where A = the American odds, b = profit per $1 staked, p = your true win probability as a fraction, and S = your stake.
Worked example
Say the odds are +110, you believe the true win chance is 52%, and you stake $50. A +110 price pays $110 profit per $100, so b = 1.10, and EV = 50 × (0.52 × 1.10 − 0.48) = 50 × (0.572 − 0.48) = 50 × 0.092 = $4.60, or about +9.2% of stake. Because your estimated probability beats the price, this is a +EV bet at your numbers.
When to use it
Use the EV calculator whenever you have an independent read on how likely an outcome is — from a model, from data, or from a sharper reference price — and want to check whether a book’s odds actually reward it. The whole exercise depends on an honest probability, which is exactly what HaterPicks’ graded player-prop models aim to provide.
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What is expected value (EV) in betting?
Expected value is the average result of a bet if you could place it many times. It weighs how much you win when it lands against how much you lose when it doesn’t, using your own estimate of the true win probability. A positive EV (+EV) bet is expected to profit on average; a negative EV (−EV) bet is expected to lose.
How do you calculate EV with American odds?
First turn the American price into profit per unit staked: b = odds ÷ 100 for a plus price, or 100 ÷ odds (ignoring the minus sign) for a minus price. So +110 gives b = 1.10 and -110 gives b = 0.909. If your true win probability is p (as a fraction) and your stake is S, then EV = S × (p × b − (1 − p)). Dividing by the stake gives EV as a percentage.
What win probability should I use?
Use your own honest estimate of how often the bet actually wins — not the sportsbook’s implied probability, which includes the vig. The calculator is only as good as that estimate, so be conservative.
Is a +EV result a guarantee?
No. EV is a long-run average and assumes your probability estimate is correct. Any single bet can lose. This tool is for research and education, not betting advice.