Understanding how to read football odds is the first skill every bettor needs. In this guide, we cover the three main odds formats used around the world and show you how to convert between them.
The Three Odds Formats
Bookmakers display odds in three formats depending on their region:
- Decimal Odds – Used in Europe, Australia and most of the world
- Fractional Odds – Traditional in the UK and Ireland
- American (Moneyline) Odds – Used in the United States
Decimal Odds (European Odds)
Decimal odds show your total return per unit staked, including your original stake.
Example: Odds of 2.50 on a $10 bet returns $25 total ($15 profit + $10 stake).
Formula: Profit = (Odds × Stake) − Stake
The 168 Index uses decimal odds as its standard format, making it easy to compare odds across 30+ bookmakers at a glance.
Fractional Odds (UK Odds)
Fractional odds show your profit relative to your stake.
Example: Odds of 3/2 on a $10 bet returns $15 profit.
Formula: Profit = (Numerator / Denominator) × Stake
| Decimal | Fractional | Implied Probability |
|---|---|---|
| 1.50 | 1/2 | 66.7% |
| 2.00 | 1/1 (Evens) | 50.0% |
| 2.50 | 3/2 | 40.0% |
| 3.00 | 2/1 | 33.3% |
| 4.00 | 3/1 | 25.0% |
American (Moneyline) Odds
American odds use a +/− system based on a $100 stake.
- Positive (+150): You win $150 profit on a $100 bet
- Negative (−200): You must bet $200 to win $100 profit
Conversion from decimal: If decimal odds are above 2.00, use Moneyline = (Decimal − 1) × 100. If below 2.00, use Moneyline = −100 / (Decimal − 1).
Implied Probability
Every set of odds implies a probability. For decimal odds:
Implied Probability = 1 / Decimal Odds × 100%
Example: Odds of 2.50 imply a 40% chance of winning (1/2.50 = 0.40).
When you add up the implied probabilities for all outcomes in a match, the total will exceed 100%. This excess is the bookmaker’s margin (also called the overround or vig).
How the 168 Index Uses Odds Data
The 168 Index collects decimal odds from over 30 international bookmakers for every match. By tracking how odds move over time, it identifies significant odds movements that signal sharp money or market consensus shifts.
Key Takeaways
- Decimal odds = total return including stake
- Fractional odds = profit only
- American odds = based on $100 unit
- All formats express the same underlying probability
- Lower odds = higher implied probability