Betting math
FreeEV & Break-Even
Expected value tells you what a bet is worth on average if your win probability is right. Enter the price and your own estimate to see the break-even rate, your edge, EV in dollars and expected ROI.
Your bet
Your own estimate, 0–100. The result depends entirely on it.
Result
Enter the odds and your own win probability.
How this works
Break-even probability = implied probability of the price = 1 / decimal odds (−110 → 52.38%).
Expected value = p(win) × profit if win − p(loss) × stake. Expected ROI = EV ÷ stake.
Probability edge = your probability − break-even. It is not the same as expected ROI: at −110, a 55% estimate is a +2.62-point probability edge but a +5.00% expected ROI.
Fair odds are the American odds at which your probability would be exactly break-even.
Pushes are ignored (win or lose only). Your estimate drives everything — an overconfident estimate produces an overconfident EV.
Questions
- Does positive EV mean the bet will win?
- No. A positive-EV bet still loses often. EV describes the long-run average across many similar bets, and only if your probability is accurate.
- What is the difference between edge and ROI?
- Edge is measured in probability points; ROI is measured as profit per dollar staked. They are shown separately because they are different numbers.
Related tools
- No-Vig / Fair OddsRemove the sportsbook's margin from a two-way (or three-way) market to get fair probabilities and odds.
- Odds ConverterConvert American, decimal and fractional odds and see the implied probability.
- Bet Quality CheckA pre-bet checklist that flags missing information, price problems and risk issues before you bet.
Read the guideExpected Value vs Probability Edge: What Bettors Confuse