Expected Value Calculator — Free EV & Betting Edge Tool
Calculate the expected value (EV) of any bet in seconds. Enter your stake, estimated win probability, and the odds (American, decimal, or fractional) to instantly see whether a bet is +EV or -EV and how much profit you expect per dollar wagered over the long run.
Odds format
Saved for all betting calculators
Amount you are betting
Your estimated win chance
e.g. -110 or +150
Expected Value
+$15.50
EV %
+15.50%
Break-even Prob.
47.62%
Potential Profit
+$110.00
Edge
+7.38 pts
Fair Odds
-122
Expected Win
+$60.50
Expected Loss
−$45.00
Payout if It Wins
$210.00
This is a +EV bet. Over many bets at these odds and probability, you expect to profit 15.50% per bet on average.
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How to Use the EV Calculator
Enter three inputs: your stake (the amount you plan to bet), your win probability as a percentage (your honest estimate of the chance you win this bet), and the odds offered by the bookmaker. Odds can be typed in American, decimal, or fractional format — pick yours once with the Odds format switch and every betting calculator opens in it.
The primary result is the Expected Value in dollars — shown in green if positive (+EV) and red if negative (−EV). You also see the EV as a percentage of your stake, the break-even probability (the minimum win rate needed to profit at these odds — the odds' implied probability) and the profit if the bet wins; if it loses, you lose the stake. A second block measures how far your probability sits above or below that break-even figure — the gap is your edge — and splits the EV into the expected win and expected loss per bet, with the fair odds at your probability and the payout if the bet wins.
A single bet result means little on its own — expected value is a long-run concept. A +EV result means that if you placed this exact bet hundreds of times, you would expect to profit on average. A −EV result means the house edge is working against you and you will lose money over time at these odds and probability.
The Formula
Expected value is calculated as the probability-weighted average of all possible outcomes:
- Define inputs:
- p = win probability (decimal, e.g. 0.55)
- q = loss probability = 1 − p
- Profit = Stake × (Decimal Odds − 1)
- Expected Value: EV = (p × Profit) − (q × Stake)
- EV %: EV% = (EV ÷ Stake) × 100
- Break-even probability: p_break = 1 ÷ Decimal Odds × 100
The break-even probability is the win rate at which EV equals exactly zero. For 2.0 decimal odds (even money), you must win 50% of the time to break even. For 2.5 odds, you need 40%. Any time your estimated win probability exceeds the break-even threshold, you have a positive expected value bet.
Note that expected value assumes your probability estimate is accurate. The quality of your EV calculation is entirely dependent on the quality of your probability estimate. Overconfident bettors consistently overestimate their win probability and therefore overestimate their EV.
Practical Examples
Example 1 — Positive EV Sports Bet
You believe a team has a 55% chance to win a game. The bookmaker prices them at 2.0 decimal odds (even money), implying only a 50% win probability. You bet $100.
- Profit if win: $100 × (2.0 − 1) = $100
- Loss if lose: −$100
- EV = (0.55 × $100) − (0.45 × $100) = $55 − $45 = +$10.00
- EV% = $10 / $100 = +10.0%
- Break-even probability: 50.0%
Your 55% estimate is 5 percentage points above the break-even threshold of 50%. Every $100 you bet at these odds and this probability yields an expected profit of $10. Over 100 such bets, you would expect to profit approximately $1,000 — though individual results will vary significantly due to variance.
Example 2 — Negative EV Parlay Leg
A bookmaker offers +250 decimal odds (3.5) on a longshot. You estimate the team has a 25% chance of winning. Stake: $50.
- Break-even probability: 1 ÷ 3.5 = 28.6%
- Profit if win: $50 × (3.5 − 1) = $125
- EV = (0.25 × $125) − (0.75 × $50) = $31.25 − $37.50 = −$6.25
- EV% = −$6.25 / $50 = −12.5%
Despite the attractive +250 odds, the bet is −EV because your estimated 25% probability falls below the 28.6% break-even threshold. The bookmaker has correctly priced the vig into this line. Placing this bet repeatedly would result in losing 12.5 cents for every dollar wagered on average.
How to Find +EV Bets in Practice
The key skill is developing win probability estimates that are more accurate than the bookmaker's implied probabilities. Professional bettors do this through statistical modeling, tracking line movement, and exploiting situations where sharp money has moved a line but a different book has not updated yet. Line shopping across multiple books is the simplest way to find +EV: if your "true" probability is 52% and one book is offering 2.05 odds (implying 48.8%), that is a mathematically positive EV bet — even without a complex model.
Frequently Asked Questions
Expected value is the average outcome of a bet if it were repeated an infinite number of times. A +EV bet means you expect to profit over the long run at those odds and probability. A −EV bet means the house edge will cost you money over time. Individual bets can win or lose regardless of their EV — expected value is a long-run concept. Professional bettors focus exclusively on finding and placing +EV bets, understanding that variance evens out over a large enough sample.
Estimating win probability accurately is the hardest part of +EV betting. Methods include: building statistical models using historical data, tracking closing line value (CLV) as a proxy for accuracy, following sharp bettors' line movements, using no-vig odds from sharp books like Pinnacle as your baseline probability estimate, and developing domain expertise in specific leagues or markets. Starting with the no-vig implied probability from a sharp book and adjusting based on your own research is a practical approach for most bettors.
The break-even probability is the minimum win rate you need at a given set of odds to have zero expected loss. It equals 1 ÷ Decimal Odds × 100. For 2.0 odds, you must win 50% of the time to break even. For -110 American odds (1.909 decimal), the break-even rate is 52.38%. Any time your true win probability exceeds the break-even threshold, you have a +EV bet. The spread between your true win probability and the break-even probability determines the size of your edge.
Yes, absolutely. Expected value is a statistical concept that only manifests over many trials. A +EV bet with a 55% win probability will still lose 45% of the time. In the short run, variance dominates — you can experience long losing streaks even with a genuine edge. This is why bankroll management (such as Kelly Criterion staking) is critical: it ensures that short-term variance does not wipe out your bankroll before the long-run EV advantage materializes.
Expected value (EV) is the theoretical long-run profit per bet based on your probability estimate, while ROI (Return on Investment) is your actual realized profit as a percentage of total stakes. EV is predictive and based on your model; ROI is historical and based on actual results. A bettor with a genuine positive EV model will eventually show positive ROI over a sufficient sample size. In the short run, ROI can diverge significantly from EV due to variance. Tracking both metrics helps distinguish skill from luck.
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