If you’ve ever looked at odds from a European sportsbook and been confused by “2.50” instead of “+150,” you’re not alone. There are three major odds formats used worldwide, and understanding all three makes you a sharper bettor.
The Three Odds Formats
American Odds (Moneyline)
The standard in the US. Displayed as positive or negative numbers centered around $100.
Positive (+150): How much profit you’d make on a $100 bet. +150 means $100 wins $150.
Negative (-200): How much you need to bet to win $100. -200 means you bet $200 to win $100.
Key insight: -110 is the most common line in US sports betting. It means you bet $110 to win $100. That extra $10 is the vig — the sportsbook’s commission.
Decimal Odds
The global standard, used in Europe, Australia, and Canada. The number represents your total return per $1 wagered (including your original stake).
2.50 means a $1 bet returns $2.50 total ($1.50 profit + $1 stake)
1.50 means a $1 bet returns $1.50 total ($0.50 profit + $1 stake)
Decimal odds are the simplest format for math because you just multiply: stake × decimal odds = total payout.
Fractional Odds
The traditional UK format, common in horse racing. Displayed as fractions like 3/1, 5/2, or 1/4.
3/1 (three-to-one): Win $3 for every $1 wagered
5/2 (five-to-two): Win $5 for every $2 wagered
1/4 (one-to-four): Win $1 for every $4 wagered
The numerator is profit, the denominator is the stake.
Conversion Formulas
American to Decimal
Positive: (American / 100) + 1 → +150 = (150/100) + 1 = 2.50
Negative: (100 / |American|) + 1 → -200 = (100/200) + 1 = 1.50
Decimal to American
Decimal ≥ 2.00: (Decimal - 1) × 100 → 2.50 = (2.50 - 1) × 100 = +150
Decimal < 2.00: -100 / (Decimal - 1) → 1.50 = -100 / (1.50 - 1) = -200
Fractional to Decimal
Divide the fraction and add 1: 3/1 = 3.0 + 1 = 4.00
Quick Reference Table
| American | Decimal | Fractional | Implied Probability |
|---|---|---|---|
| -500 | 1.20 | 1/5 | 83.3% |
| -200 | 1.50 | 1/2 | 66.7% |
| -110 | 1.909 | 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% |
| +500 | 6.00 | 5/1 | 16.7% |
Why This Matters for Betting
Understanding odds formats isn’t just trivia. It’s practical:
Line shopping across regions: The best odds might be at a European book showing decimal format. If you can’t read them, you’ll miss value.
Probability intuition: Decimal odds make it easy to estimate implied probability at a glance. Just take 1 divided by the decimal odds.
Faster math: When calculating parlays or expected value, decimal odds are far easier to work with than American odds.
Key Takeaways
American odds show profit relative to $100, decimal shows total return per $1, fractional shows profit ratio
Decimal is the easiest format for calculations — multiply stake by odds for total payout
Being fluent in all three formats lets you shop lines across international sportsbooks
Use the odds converter whenever you need a quick translation between formats
