Expected value formula
EV = win probability × profit if win - lose probability × stake
Strategy Tools
LiveExpected Value Calculator | EV Betting Tool | XYES
Free EV betting calculator: enter stake, odds and estimated win probability to check expected value, break-even probability and long-term edge.
Positive / negative EVBreak-even probabilityFree · no signup
EV calculator
Enter stake, odds and your estimated win probability
Supports decimal, fractional and American odds. The result shows break-even probability, EV amount, EV percentage and edge.
Common scenarios
Start with a realistic example, then replace it with the price you are evaluating.
Odds format
Live result
Positive EV
$9.20
9.20%
Break-even line
47.62%
Probability edge
4.38%
Profit if win / Loss if lose
Profit if win
$110.00
Loss if lose
$100.00
Positive EV
Next step：Confirm the price is still available, then use conservative staking. Positive EV is a long-term estimate, not a guarantee for this bet.
EV amount
$9.20
EV percentage
9.20%
Break-even probability
47.62%
Probability edge
4.38%
Profit if win / Loss if lose
Profit if win
$110.00
Loss if lose
$100.00
Probability comparison
4.38%
Your estimate 52.00% · Break-even line 47.62%
Your estimate
52.00%
Break-even line
47.62%
Decimal odds: 2.100
Your estimated win probability is 52.00%; break-even probability is 47.62%. The smaller the gap, the more conservative your stake should be.
Important note
EV is a mathematical estimate, not a prediction that this bet will win. Before betting real money, consider limits, price movement, market quality, terms and your own risk tolerance.
How to use it
How to use the EV calculator before placing a bet
Enter stake, odds and your estimated win probability, then compare the result with break-even probability to judge whether the bet is positive EV or negative EV.
- 1
Enter stake and odds
Choose decimal, fractional or American odds, then enter the stake and price you want to evaluate.
- 2
Enter your estimated win probability
Use a conservative probability estimate. This input drives the EV result.
- 3
Check EV amount and break-even probability
Compare your estimate with the break-even probability, EV amount, EV percentage and probability edge.
- 4
Retest with a conservative estimate
Lower your probability estimate by 1% or 2%. If the result flips, the edge is too thin.
Formula and example
How does the EV betting formula work?
The calculator uses one core formula: multiply the profit if the bet wins by your estimated win probability, then subtract the chance-weighted loss if it loses.
Break-even probability
Break-even probability = 1 ÷ decimal odds
Fractional conversion
Fractional 11/10 = decimal odds 2.10
Quick example: $100 · 2.10 · 52%
- At decimal odds 2.10, a $100 stake returns $110 profit if it wins and loses $100 if it loses.
- Break-even probability = 1 ÷ 2.10 = 47.62%.
- If your estimated win probability is 52%, EV = 52% × $110 - 48% × $100 = $9.20.
- EV percentage = $9.20 ÷ $100 = 9.20%, which is positive EV under this assumption.
Read the result
After calculating EV, check these three signals
Start with break-even probability
Your estimated win probability must be higher than the break-even line before the price has positive EV potential.
Then check EV percentage
EV percentage shows the theoretical return relative to stake. A result near 0% is too thin to treat aggressively.
Stress-test your estimate
Reduce your win probability by 1% or 2%. If positive EV disappears immediately, the margin of safety is weak.
Strategy context
How to read positive EV and negative EV
EV does not predict the next result. It asks whether the odds compensate you for the risk if a similar bet were repeated many times. The key question is not how high the payout looks, but whether your win probability estimate is above the break-even probability implied by the odds.
Football at 2.10 decimal odds
If you estimate a 52% win probability and the break-even line is 47.62%, the bet has positive EV potential, assuming your estimate is well supported.
Even-money casino bets
A bet may look close to 50/50, but games with house edge still reduce long-term EV. Always compare the true probability with the payout.
High-priced underdogs
+300 American odds need a 25% break-even probability. If your true estimate is only 20%, the payout is still negative EV.
FAQ
Expected value calculator questions
EV formula, break-even probability, odds formats, staking risk and RTP, explained in plain English.
What does EV mean in betting?
EV means expected value. In betting, it combines the potential profit, the amount you can lose and your estimated win probability to show whether similar bets would theoretically average a profit or loss over time.
Does positive EV mean this bet will win?
No. Positive EV only means the long-term theoretical average is positive under your assumptions. A single bet can still lose, and your estimate can be wrong. Price movement, limits, market quality and staking discipline all matter.
How do you calculate break-even probability?
For decimal odds, break-even probability is 1 divided by the decimal odds. For example, 2.00 needs 50%, 2.50 needs 40%, and 2.10 needs about 47.62%. Your estimated win probability must be above this line for positive EV.
What is the betting EV formula?
The core formula is EV = win probability × profit if win - lose probability × stake. Example: $100 stake, 2.10 decimal odds and a 52% win estimate gives EV = 52% × $110 - 48% × $100 = $9.20.
Can I use American odds or fractional odds?
Yes. The calculator converts American odds and fractional odds into decimal odds before calculating EV. For example, +110 and 11/10 both equal 2.10 decimal odds.
How much should I stake on a positive EV bet?
Positive EV does not automatically mean you should bet big. Retest with a conservative probability, consider bankroll size, market limits and volatility, then choose a stake you can tolerate if the bet loses.
What is a good EV percentage in betting?
There is no universal good EV percentage because it depends on confidence in your probability estimate, market liquidity, limits and variance. A small positive EV can disappear if your estimate is slightly too high, so treat thin edges conservatively.
How is EV different from bookmaker margin?
Bookmaker margin measures how much the odds are shaded across a market. EV measures whether one specific price is still valuable after comparing the implied probability with your own win-probability estimate.
What is the difference between EV and RTP?
EV is usually applied to a specific bet or betting assumption. RTP is the long-term theoretical return of a game, often used for slots and table games. Both are long-term concepts, not short-term guarantees.
Can EV be used for sports betting and casino games?
Yes, but the inputs differ. Sports betting usually requires your own win-probability estimate. Casino examples often use known probabilities and payout rules, though most casino games include a built-in house edge.
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