Betting Odds Converter
Convert odds between American, Decimal, and Fractional formats. Calculate implied probability, expected value, and optimal bet size with Kelly criterion.
Enter Odds
Expected Value Calculator
American
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Decimal
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Fractional
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Implied Probability
The probability implied by the bookmaker's odds (includes vig/margin)
Expected Value (EV)
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Enter your estimated probability above
Kelly Criterion Bet Size
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Optimal bet as % of bankroll
Payout Breakdown
Bet Amount
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Profit if Win
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Total Payout
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Saved Calculations
Quick Reference: Common Odds
| American | Decimal | Fractional | Implied Prob. | $100 Profit |
|---|---|---|---|---|
| -500 | 1.20 | 1/5 | 83.3% | $20 |
| -200 | 1.50 | 1/2 | 66.7% | $50 |
| -110 | 1.91 | 10/11 | 52.4% | $91 |
| +100 | 2.00 | 1/1 | 50.0% | $100 |
| +150 | 2.50 | 3/2 | 40.0% | $150 |
| +300 | 4.00 | 3/1 | 25.0% | $300 |
| +1000 | 11.00 | 10/1 | 9.1% | $1,000 |
Understanding Betting Odds Formats
American Odds
Used primarily in the US. Positive odds (+150) show profit on a $100 bet. Negative odds (-200) show how much you need to bet to win $100. The favorite always has negative odds; the underdog has positive odds.
Decimal Odds
Popular in Europe and Australia. The number represents total payout per dollar wagered (including your stake). Decimal 2.50 means $2.50 returned for every $1 bet. Easier to compare across markets.
Implied Probability & Edge
Implied probability = 1 / decimal odds. This tells you what win rate you need to break even. If your estimated probability exceeds the implied probability, you have a positive expected value bet.