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Odds Converter: American, Decimal, and Fractional Odds Calculator
Last Updated: March 4, 2026
Odds formats differ by region, but the underlying math is identical. The converter above translates between American, decimal, and fractional odds instantly, and outputs the implied probability for each. Enter any odds value in one format, and the tool calculates the equivalent in all others — no manual formulas required.
How Do You Use the Odds Converter?
Enter your odds in any of the three input fields — American, decimal, or fractional — and the tool populates the remaining formats automatically. The implied probability output shows the win percentage the odds represent before vig removal.
Three practical uses:
- Cross-format comparison. European sportsbooks display decimal odds; US books use American. If you see 1.91 at a European exchange and -110 at a US sportsbook, the converter confirms they are the same price.
- Probability extraction. Converting -150 reveals a 60% implied probability. Comparing that to your own estimate tells you whether the bet has positive expected value.
- Prediction market bridging. A prediction market contract at $0.40 implies 40% probability. The converter shows this equals +150 American or 2.50 decimal — useful when comparing sportsbook lines against prediction market prices.
How Do You Interpret the Results?
The converter returns four values for every input: American odds, decimal odds, fractional odds, and implied probability. Each represents the same underlying price in a different notation.
Decimal odds are the most intuitive for calculations. They represent total return per dollar wagered. Multiply your stake by the decimal odds to get total payout. Subtract the stake for profit.
American odds are standard at US sportsbooks. Positive values show profit on a $100 stake. Negative values show the stake required to profit $100.
Fractional odds are common in UK horse racing and soccer. The numerator is profit; the denominator is stake. 3/1 means $3 profit for every $1 wagered.
Implied probability is the percentage chance the odds assign to the outcome. This is the number that matters most for value analysis — compare it against your own probability estimate to find edges. For a deeper explanation, see implied probability and how to calculate it.
What Does a Worked Conversion Look Like?
The table below shows equivalent values across all four representations for common odds:
| American | Decimal | Fractional | Implied Probability | Bet $100 Profit |
|---|---|---|---|---|
| -300 | 1.33 | 1/3 | 75.0% | $33.33 |
| -200 | 1.50 | 1/2 | 66.7% | $50.00 |
| -150 | 1.67 | 2/3 | 60.0% | $66.67 |
| -110 | 1.91 | 10/11 | 52.4% | $90.91 |
| +100 | 2.00 | 1/1 (Evens) | 50.0% | $100.00 |
| +150 | 2.50 | 3/2 | 40.0% | $150.00 |
| +200 | 3.00 | 2/1 | 33.3% | $200.00 |
| +300 | 4.00 | 3/1 | 25.0% | $300.00 |
| +500 | 6.00 | 5/1 | 16.7% | $500.00 |
Notice that -110 (standard US juice) equals 1.91 decimal — not 2.00. That gap between 1.91 and 2.00 is the vig. A fair coin-flip bet would pay 2.00 decimal (+100 American). The sportsbook’s margin lives in that 0.09 difference.
Why Does Odds Conversion Matter for Prediction Markets?
Prediction market contracts trade at prices between $0.01 and $0.99, where the price directly represents implied probability. A contract at $0.65 means 65% — no conversion needed. But comparing that 65% against a sportsbook line requires translating between systems.
If a sportsbook posts -200 on the same outcome, the implied probability is 66.7%. The prediction market says 65%; the sportsbook says 66.7%. That 1.7-point spread reflects the sportsbook’s vig plus any genuine disagreement between markets. Identifying these gaps is the foundation of cross-market analysis.
The Odds Reference dashboard tracks thousands of markets across prediction platforms and sportsbooks. Odds conversion is the bridge that makes those comparisons meaningful. Our data across both verticals shows where sportsbook lines and prediction market prices diverge — and by how much.
For calculating combined odds across multiple bets, use the parlay calculator. For a full primer on reading odds, start with how to read betting odds.
Key Takeaways
- American, decimal, and fractional odds are three representations of the same underlying probability
- Decimal odds are the simplest for payout calculation: multiply by stake for total return
- Implied probability is the critical output — compare it to your own estimate to identify value bets
- Prediction market prices are already implied probabilities; odds conversion bridges them to sportsbook lines
- The gap between formats often reveals the vig — the sportsbook’s built-in margin