Expected Value Calculator: Is This Bet Worth Making?

Expected value is the average result of a bet if you could place it thousands of times. Positive EV means the price pays more than the true chance justifies. Negative EV means the sportsbook has the edge. Enter the odds, your stake and your win probability below to see what a bet is worth.

The expected value formula

EV = (p × profit) − ((1 − p) × stake)

• p is your estimated probability of winning
• profit is what you win on top of your stake
• stake is what you lose if the bet fails

As a percentage of stake: EV% = (p × decimal odds) − 1.

Worked example: an underdog at +150

You stake $100 on an underdog at +150. The sportsbook’s price implies 40%. Your model says 45%.

• Profit if it wins: $150
• EV = (0.45 × $150) − (0.55 × $100) = $67.50 − $55.00 = +$12.50
• EV% = (0.45 × 2.50) − 1 = +12.5%

Now the same bet at -110 on a 50/50 game:

• EV = (0.50 × $90.91) − (0.50 × $100) = −$4.55

That −4.5% is the vig at work. On a true coin flip at -110, you lose about $4.55 per $100 over time.

Where the probability comes from

EV is only as good as your p. Professional +EV bettors rarely invent it. They borrow it from the market.

1. Take the price at a sharp sportsbook or exchange.
2. Remove the vig to find the fair probability. Our implied probability calculator does this.
3. Find a slower book offering a better price than that fair number.

That is what tools such as OddsJam, Unabated and Outlier Pro automate. Compare them in our AI sports betting tools ranking.

When to use an EV calculator

• Before any bet you think is value. If EV is negative at your own estimate, there is nothing to stake.
• On boosts and promos. A profit boost raises the payout. Plug in the boosted odds to see if the bet turns positive.
• On prediction markets. A Kalshi contract at 38 cents that you rate at 45% has positive EV before fees. Subtract the fee from your profit. See our Kalshi review.
• Before staking. Positive EV tells you to bet. Our Kelly criterion calculator tells you how much.

Remember that positive EV is a long-run edge. Even a +12.5% bet loses more often than it wins at +150, so judge results over hundreds of bets, not a weekend.

Common EV mistakes

• Confusing hit rate with value. A bet can win 70% of the time and still be negative EV at a short enough price.
• Overrating your own estimate. If your probability is just your gut feeling, your EV is too. Test any model against closing prices first. Our guide to AI prediction sites shows how.
• Judging results too soon. Variance swamps edge over short runs. A +3% EV bettor can easily be down after 100 bets.
• Forgetting fees and limits. Exchange commission and prediction market fees come off the profit line. A +EV bet you can only stake $20 on is worth $20 of edge.

See all our free betting calculators.

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