Sports Betting 101
beginner6 min read
How to Read Odds: American, Decimal, and Fractional Explained
A complete guide to understanding the three major odds formats used in sports betting worldwide.
How to Read Odds
Odds are the language of sports betting. They tell you two things: how much you can win and the implied probability of an outcome. There are three major formats used worldwide.
American Odds
The standard in the US. Expressed as positive or negative numbers.
Negative odds (-150): How much you must bet to win $100
- Bet $150 to win $100 (total return: $250)
Positive odds (+150): How much you win on a $100 bet
- Bet $100 to win $150 (total return: $250)
Decimal Odds
Popular in Europe, Australia, and Canada. The number represents your total return per $1 wagered.
- 2.50 means you get $2.50 back for every $1 bet (including your stake)
- Profit = (Decimal Odds - 1) × Stake
Fractional Odds
Traditional in the UK, especially for horse racing.
- 3/1 means you win $3 for every $1 bet
- 1/4 means you win $1 for every $4 bet
Conversion Table
| American | Decimal | Fractional | Implied Prob |
|---|---|---|---|
| -200 | 1.50 | 1/2 | 66.7% |
| -150 | 1.67 | 2/3 | 60.0% |
| -110 | 1.91 | 10/11 | 52.4% |
| +100 | 2.00 | 1/1 | 50.0% |
| +150 | 2.50 | 3/2 | 40.0% |
| +200 | 3.00 | 2/1 | 33.3% |
| +300 | 4.00 | 3/1 | 25.0% |
Converting Between Formats
American to Decimal:
- Positive: (American/100) + 1
- Negative: (100/|American|) + 1
Decimal to Implied Probability:
- 1/Decimal Odds × 100
Mastering odds conversion is the first step to understanding value in sports betting.