How to Read Betting Odds (American, Decimal & Fractional)
Understand American, decimal, and fractional odds, what favorites and underdogs look like, and how to convert odds to payouts and probabilities.
Odds are the language of betting. They do two jobs at once: they tell you your payout and they imply a probability. There are three common formats - American, decimal, and fractional - and they all describe the same thing.
American odds
American odds are built around $100. A negative number is a favorite and shows how much you must risk to win $100. A positive number is an underdog and shows how much you win on a $100 bet.
- −150 → risk $150 to win $100 (favorite).
- +130 → risk $100 to win $130 (underdog).
- −110 → the standard price on a coin-flip market; risk $110 to win $100.
Decimal odds
Common in Europe, Australia, and on betting exchanges, decimal odds show your total return per $1 staked, including your stake. Multiply your stake by the decimal to get your payout.
- 2.00 = even money (bet $1, get $2 back).
- 1.67 ≈ −150 in American.
- 2.30 ≈ +130 in American.
Fractional odds
Traditional in the UK and horse racing, fractional odds like 6/4 show profit relative to stake: a $4 bet profits $6. They're the least useful format for quick math, but you'll see them at some books.
Converting odds to probability
Every price implies a probability. For decimal odds, implied probability = 1 ÷ decimal. So 2.00 implies 50%, and 1.67 implies about 60%. Converting odds to probability is the single most important habit in betting - it's how you tell whether a price is generous or a trap. We cover this in depth in Implied Probability.
Quick reference
| American | Decimal | Implied % |
|---|---|---|
| −200 | 1.50 | 66.7% |
| −150 | 1.67 | 60.0% |
| −110 | 1.91 | 52.4% |
| +100 | 2.00 | 50.0% |
| +130 | 2.30 | 43.5% |
| +200 | 3.00 | 33.3% |
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