Free Betting Odds Calculator
Convert between American, decimal, and fractional odds. Calculate payouts, implied probability, and expected value — instantly, for free.
Payout Calculator
Expected Value Calculator
How to Use the Odds Calculator
Enter odds in any format and the calculator instantly converts to all three major formats: American, decimal, and fractional. American odds are the standard in US sportsbooks — positive numbers (+150) indicate the profit on a $100 bet, while negative numbers (-200) show how much you need to bet to profit $100. Decimal odds multiply your stake by the decimal value to get total payout. Fractional odds show the ratio of profit to stake.
Understanding Implied Probability
Every set of odds has an implied probability — the break-even win rate for that bet. If the odds imply 40% probability but your model gives the outcome a 50% chance, that's a positive expected value bet. Our AI prediction models for NFL, NHL, Tennis, and March Madness generate win probabilities you can compare against implied odds to find +EV bets.
Expected Value (EV) Explained
Expected value is the single most important concept in sports betting. It measures your average profit or loss per bet over time. EV = (Win Probability × Profit) - (Loss Probability × Stake). Professional bettors ignore individual results and focus entirely on making +EV bets consistently. Enter your estimated win probability above to calculate the EV of any bet.
American vs Decimal vs Fractional Odds
| Format | Example | Payout on $100 | Common In |
|---|---|---|---|
| American | +150 | $250 | United States |
| Decimal | 2.50 | $250 | Europe, Australia |
| Fractional | 3/2 | $250 | United Kingdom |
Frequently Asked Questions
What are American odds?
American odds use a plus (+) or minus (-) sign. Positive odds (+150) show how much profit you'd make on a $100 bet. Negative odds (-200) show how much you need to bet to profit $100.
How do you convert American odds to decimal?
For positive: Decimal = (American / 100) + 1. For negative: Decimal = (100 / |American|) + 1. Example: +150 = 2.50, -200 = 1.50.
What is implied probability?
Implied probability is the break-even win rate suggested by the odds. If odds imply 40% but you estimate 50%, the bet has positive expected value.
What is expected value (EV)?
EV measures average profit/loss per bet over time. Positive EV means the bet is profitable long-term. Formula: (Win% × Profit) - (Loss% × Stake).
Want AI-Calculated Win Probabilities?
Our AI models generate win probabilities for NFL, NHL, Tennis, and March Madness. Compare them against implied odds to find +EV bets — all for 99¢ per sport.
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