Sports Betting 101
beginner5 min read
Understanding Odds: American, Decimal, and Fractional
Learn how to read and convert between the three major odds formats used worldwide.
Understanding Odds Formats
Odds are the language of sports betting. They tell you two things: the implied probability of an outcome and how much you'll be paid if you win.
American Odds
The most common format in the United States:
- Negative (-) odds show how much you must bet to win $100
- Positive (+) odds show how much you win on a $100 bet
Example: -150 means bet $150 to win $100. +200 means bet $100 to win $200.
Decimal Odds
Popular in Europe, Australia, and Canada:
- Your total return = stake × decimal odds
- Example: 2.50 odds on a $100 bet returns $250 ($150 profit + $100 stake)
Fractional Odds
Traditional format in the UK:
- 5/2 means you win $5 for every $2 wagered
- Example: $100 at 5/2 returns $350 ($250 profit + $100 stake)
Conversion Formulas
| From | To American | To Decimal | To Fractional |
|---|---|---|---|
| American (+) | — | (odds/100) + 1 | odds/100 |
| American (-) | — | (100/ | odds |
| Decimal | (dec-1)×100 if >2.0 | — | (dec-1)/1 |
Understanding all three formats is essential because different sportsbooks and regions use different formats.