Expected Value (EV) Calculator for Betting

What Is Expected Value in Betting?

Expected value (EV) measures how much you can expect to win or lose per bet on average over the long run. A positive EV (+EV) bet means you expect to profit over time. A negative EV (-EV) bet means the house or bookmaker has the edge.

Every casino game has a negative expected value for the player — that's the house edge. Sports betting is different: because odds are set by market forces, not fixed math, it's possible to find bets where your estimated probability of winning is higher than what the odds imply. Those are +EV bets.

The formula is straightforward:

EV = (Win Probability × Profit if You Win) − (Loss Probability × Amount You Lose)

For example, if you bet $100 at decimal odds of 2.50 and you estimate a 45% chance of winning:

• Profit if you win: $150 (2.50 × $100 − $100)

• EV = (0.45 × $150) − (0.55 × $100) = $67.50 − $55.00 = +$12.50 per bet

That means if you made this exact bet thousands of times, you'd average $12.50 profit per bet.

How to Use This Calculator

1. Select your odds format — American (+150), Decimal (2.50), or Fractional (3/2)

2. Enter the odds offered by the bookmaker or casino

3. Estimate your win probability — what you honestly think the true chance is (not what you hope)

4. Enter your stake — the amount you plan to bet

5. Read the results — the calculator shows your EV per bet, edge percentage, implied probability, and whether the bet is +EV or -EV

The hardest part is step 3: estimating true probability honestly. The calculator can't do that for you — it depends on your research, models, or expertise in the sport or game.

EV vs Kelly Criterion

This calculator tells you whether a bet is worth taking. The Kelly Criterion Calculator tells you how much to bet once you've found a +EV opportunity.

Use them together:

1. Find a potential bet → check EV here → if it's +EV, then

2. Use the Kelly Calculator to size the bet optimally

When EV Matters (and When It Doesn't)

EV is a long-run concept. One bet can go either way regardless of its EV. Where EV becomes powerful is over hundreds or thousands of bets — the math converges and +EV bettors profit while -EV bettors lose.

For casino games, the EV is fixed and negative (that's the house edge by definition). You can't change it. For sports betting, EV depends on finding lines where the bookmaker's implied probability is lower than reality. That's the entire premise of value betting.

Frequently Asked Questions

What does +EV mean?

Positive expected value (+EV) means you expect to profit per bet on average over the long run. It doesn't guarantee you'll win any single bet — just that the math is in your favor if you make the same type of bet repeatedly.

What does -EV mean?

Negative expected value (-EV) means you expect to lose per bet on average. Every standard casino game is -EV for the player. Most sports bets at market odds are also slightly -EV because the bookmaker builds in a margin (the vig).

How do I estimate my true win probability?

This is the hard part. For sports, you can build statistical models, compare multiple bookmaker odds (the market consensus), or use historical data. For casino games, the probabilities are mathematically fixed — check the game's rules and house edge.

Can I find +EV bets consistently?

Professional sports bettors do, but it requires significant skill, research, and discipline. The bookmaker's odds already reflect substantial analysis. Finding genuine +EV means knowing something the market doesn't, or finding stale lines before they move.

How is EV related to the house edge?

The house edge is simply the negative EV expressed as a percentage of the bet. A game with a 5% house edge has an EV of -$5 per $100 bet. The calculator shows this relationship directly.

Sources

• Expected Value — Khan Academy

• Value Betting Explained — Wild.io Academy

• Kelly Criterion Calculator — Wild.io Academy