Odds Converter: Decimal, Fractional & American
Quick take: Sportsbooks display odds in different formats depending on region — decimal (Europe), fractional (UK/Ireland), and American (US). This converts instantly between all three and shows the implied probability behind them. No signup, no download.
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Implied probability
45.5%
The bookmaker’s break-even probability at these odds, before their margin.
The Three Odds Formats, Compared
| Format | Example | Common in | Reads as |
|---|---|---|---|
| Decimal | 2.20 | Europe, Australia, Canada | Total payout per $1 staked, including your stake back |
| Fractional | 6/5 | UK, Ireland | Profit relative to stake — win $6 for every $5 staked |
| American | +120 / −110 | United States | + shows profit on a $100 bet; − shows stake needed to profit $100 |
What “Implied Probability” Means
Every set of odds implies a probability — the break-even chance of that outcome, from the bookmaker’s point of view. At decimal odds of 2.20, for example, the implied probability is 100 ÷ 2.20 = 45.5%. This number is useful for one specific thing: comparing it against your own probability estimate to see if a bet has value. If you think the true chance is higher than the implied probability, that’s the basic definition of a value bet — covered in more depth in our predictions guide.
One caveat worth knowing: implied probability calculated this way doesn’t account for the bookmaker’s built-in margin (the “vig” or “overround”), so the real fair probability is usually slightly lower than what a single set of odds implies.
Frequently Asked Questions
Why does my sportsbook show a different fraction than this tool? This converter shows the mathematically exact fraction. Some sportsbooks round to conventional “nicer” fractions (e.g. 10/11 instead of the exact 91/100 for 1.91 decimal) — both represent essentially the same odds, just displayed differently.
Which odds format should I use? Whichever your sportsbook displays natively. There’s no mathematical advantage to one format over another — they’re just different ways of expressing the same number.
What does a negative American odds number mean? Negative American odds (e.g. −110) show the underdog’s favorite — you’d need to stake $110 to profit $100. Positive odds (e.g. +120) show how much profit a $100 stake would return.
Can I use this for arbitrage or value-bet calculations? Yes — converting all your odds to the same format (usually decimal) is the first step for both. See our arbitrage betting guide for the full calculation.
Does implied probability tell me if a bet is good? Not on its own — it only tells you what the bookmaker’s odds assume. You still need your own estimate of the real probability to know whether there’s value; see our Sports Investing Bible for that framework.
Related tools and guides
- Size your stake correctly with our Kelly Criterion Calculator.
- Understand value betting in our Sports Investing Bible.
- Learn guaranteed-profit strategies in our Arbitrage Betting Guide.