The EV Calculator compares the bookmaker’s odds with your fair (true) odds and estimates your expected profit or loss and edge (%) for the bet. Positive EV suggests long-term value; negative EV signals an expected loss. Use it to screen bets and size stakes responsibly.
An EV calculator tells you how much a bet is worth on average before you place it. Enter the odds you are offered, your estimate of the true (fair) odds and your stake, and the calculator returns the expected value in money and as a percentage of the stake.
Expected value (EV) is the average profit or loss a bet would return if you could place it many times at the same price and probability. A positive EV bet is priced better than its true chance of winning; a negative EV bet is priced worse. EV describes the long run: any single positive EV bet can still lose.
With p as the true probability of winning:
True probability (p) = 1 ÷ true odds
EV = p × (offered odds − 1) × stake − (1 − p) × stake
which simplifies to: EV = (offered odds ÷ true odds − 1) × stake
EV % = (offered odds ÷ true odds − 1) × 100All odds are decimal. The calculator uses the simplified form, so EV % is your edge per unit staked.
| Offered odds | True odds | Stake | EV | EV % |
|---|---|---|---|---|
| 2.20 | 2.00 (50%) | $100 | +$10.00 | +10% |
| 2.10 | 2.00 (50%) | $50 | +$2.50 | +5% |
| 1.90 | 2.00 (50%) | $100 | −$5.00 | −5% |
In the first row the bet wins half the time: +$120 × 50% − $100 × 50% = +$10 per bet on average.
EV is only as accurate as the true odds you enter. Small errors in the probability estimate can turn a positive EV bet into a negative one, so conservative estimates are safer.
A prediction-market share price converts to decimal odds with 1 ÷ price. A share bought at 0.45 is 2.222 in decimal odds; if you estimate the true probability at 50% (true odds 2.00), EV is (2.222 ÷ 2.00 − 1) = +11.1% before fees.
Finding positive EV bets by hand means checking many markets against fair odds. OddsFantasy's positive EV tool compares prices against no-vig odds from sharp bookmakers such as Pinnacle, and positive EV automation can place qualifying bets on Polymarket automatically using your EV, odds, sport, spread, volume and stake filters.
Any positive EV is favourable in theory, but small edges are easily wiped out by errors in your true odds, fees, limits and slippage. Many bettors therefore require a margin of safety above zero before betting.
No. EV is a long-run average. Individual results vary, and a positive EV bettor can still have losing streaks; the EV simulator shows how wide that variance can be.
EV is the average profit in money for your stake. EV % is the same edge per unit staked, which makes bets of different sizes comparable.
The calculator expects decimal odds. Convert American odds with 1 + 100 ÷ |odds| for negative odds and 1 + odds ÷ 100 for positive odds.