Odds Converter
Convert betting odds between decimal, American, fractional, and implied probability in real time. Type any value — the other three update instantly. Used by value bettors to compare prices across global sportsbooks.
Conversion Formulas
All four formats describe the same underlying payout — they're just different notations. Here's the math behind the converter:
implied_probability = 1 / decimal_oddsDecimal 2.50 → 1/2.50 = 0.40 = 40% implied probability.
american = (decimal − 1) × 100 if decimal ≥ 2.00american = −100 / (decimal − 1) if decimal < 2.00Decimal 2.50 → (2.50 − 1) × 100 = +150. Decimal 1.50 → −100/0.50 = −200.
fractional = decimal − 1 (expressed as a simplified ratio)Decimal 2.50 → 2.50 − 1 = 1.5 = 3/2. Decimal 3.00 → 2 = 2/1.
Reference Table
| Decimal | American | Fractional | Implied % | Profit on $100 |
|---|---|---|---|---|
| 1.20 | −500 | 1/5 | 83.33% | $20.00 |
| 1.50 | −200 | 1/2 | 66.67% | $50.00 |
| 1.75 | −133 | 3/4 | 57.14% | $75.00 |
| 1.91 | −110 | 10/11 | 52.38% | $91.00 |
| 2.00 | +100 | 1/1 (evens) | 50.00% | $100.00 |
| 2.50 | +150 | 3/2 | 40.00% | $150.00 |
| 3.00 | +200 | 2/1 | 33.33% | $200.00 |
| 5.00 | +400 | 4/1 | 20.00% | $400.00 |
| 10.00 | +900 | 9/1 | 10.00% | $900.00 |
| 21.00 | +2000 | 20/1 | 4.76% | $2000.00 |
How Bettors Use This
The implied probability is the most useful output. It tells you the bookmaker's price for an outcome — independent of format. Once you have it:
- Compare with your model: if your true probability is higher than the implied, the bet has positive expected value (EV calculator).
- Remove the vig: raw implied probabilities sum to over 100% — the overround is the bookmaker margin. See our methodology for no-vig calculations.
- Compare prices across books: a +150 line at DraftKings might be +165 at FanDuel — 8% higher implied probability gap, free EV.
- Build parlays correctly: multiply decimal odds together for total parlay payout (parlay calculator).
Worked Examples
Three real-world scenarios bettors face every day. Each shows the conversion in context.
Example 1 — Cross-book price comparison (NFL spread)
DraftKings offers Chiefs −3.5 at −110 (American). FanDuel offers the same line at −105. Which is better, and by how much?
−105 → decimal 1.952 → implied 51.22%
Edge from price shopping: +1.16 pp of implied probability — roughly +2.2% EV just by choosing the right book.
Over 1,000 bets at $100 each, that −2.2% saving compounds to $2,200 extra profit with zero handicapping skill. This is why sharp bettors maintain accounts at 6–10 books.
Example 2 — Soccer 1X2 vig calculation
Bet365 prices a Premier League match: Home 2.20, Draw 3.30, Away 3.40 (decimal). Sum of implied probabilities:
Overround = 5.17% — the bookmaker's built-in margin.
No-vig fair probabilities: Home 43.22%, Draw 28.81%, Away 27.97% (each implied / 1.0517).
If your model says Home should be 47%, that's a +3.78 pp edge over the fair price, not the raw implied 45.45%. Always de-vig before computing EV.
Example 3 — Fractional to decimal (UK horse racing)
A horse is listed at 9/4 with William Hill. Converting:
3.25 → implied probability 1/3.25 = 30.77%
3.25 → American: (3.25 − 1) × 100 = +225
If you found the same horse at +240 on a US-facing book, that's decimal 3.40, implied 29.41%, or a +1.36 pp edge from format arbitrage alone.
Glossary of Odds Terms
- Decimal odds: the total payout per 1 unit staked (including the stake). Standard in Europe, Australia, Canada. Example: 2.50 means $2.50 returned on every $1 wagered.
- American odds: moneyline format. Positive numbers (e.g. +150) show profit on a $100 bet; negative numbers (e.g. −200) show stake required to win $100.
- Fractional odds: profit-to-stake ratio. 5/2 means $5 profit per $2 staked. Standard in UK, Ireland, and horse racing globally.
- Implied probability: the probability of an outcome as priced by the bookmaker. Formula: 1 / decimal_odds. Always includes the bookmaker's vig.
- Vig / juice / overround: the bookmaker's built-in margin. Sum of all outcome implied probabilities minus 100%.
- No-vig probability: the fair (true) probability after removing the bookmaker's margin. Each raw implied probability divided by the overround sum.
- Push: a tie outcome (e.g. exact spread hit). Stakes are refunded; bet treated as if it never happened.
- Steam move: rapid line movement caused by sharp money. Often signals the closing line will move further — grab the early price.
- Closing line value (CLV): the difference between the odds you bet and the final price at kickoff. Beating the close consistently is the strongest predictor of long-term profit.
A Brief History of Betting Odds Formats
Different formats evolved from different gambling cultures.
Fractional odds originated in 18th-century English horse racing. Bookmakers shouted prices like "five to one" — a natural verbal format when stakes and payouts were quoted separately. The UK kept this tradition long after the rest of Europe moved on.
Decimal odds rose with European football pools and the introduction of computer-driven sportsbooks in the 1980s–1990s. Decimal removes the mental math — just multiply your stake by the odds to see your total return. Today decimal is the global default outside the US and UK.
American odds are a quirk of US sportsbooks that historically quoted vig in dollar terms. A −110 line literally means "risk $110 to win $100" — a direct expression of the standard −4.55% house edge on a balanced market. Despite the format's awkwardness, US books retain it for tradition and to obscure the vig from casual bettors.
Implied probability became standard analytical language after the rise of Pinnacle and the sharp-betting forums in the early 2000s. Every modern sports-betting model speaks in probabilities first, prices second.
Frequently Asked Questions
How do I convert decimal odds to American odds?
For decimal odds ≥ 2.00: American = (decimal − 1) × 100. For decimal odds < 2.00: American = −100 / (decimal − 1). Example: 2.50 → +150, 1.50 → −200.
What is implied probability?
Implied probability is the probability an outcome happens, as priced by the bookmaker. Formula: implied = 1 / decimal_odds. Example: odds of 2.00 = 50% implied probability. If your true probability is higher than the implied, the bet has positive EV.
Why do bookmakers use different odds formats?
Decimal odds are standard in Europe, Australia, and Canada. American odds are used in the US. Fractional odds are traditional in UK and Ireland. All three represent the same payout — the format is just regional preference.
How accurate is implied probability for predicting outcomes?
Raw implied probability includes the bookmaker's margin (vig), so it sums to over 100% across all outcomes. To get a fair estimate, you need no-vig (true) probability — see our EV Calculator and methodology.
Find bets where your edge beats the implied probability
EVBets scans 94 bookmakers every 30 minutes and finds outcomes where the no-vig probability is higher than the priced-in implied — pure positive EV.
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