How to Read Betting Odds — American, Decimal, and Fractional Explained
Comprehensive guide to reading betting odds in all three formats: American (+/-), decimal (2.50), and fractional (3/2). Learn how to convert between formats and calculate potential payouts.
The Three Odds Formats
Betting odds are displayed in three main formats around the world. American odds (also called moneyline odds) use a plus/minus system: +150 means a $100 bet wins $150, while -150 means you must bet $150 to win $100. Decimal odds (popular in Europe and Australia) show your total return per unit staked — a 2.50 decimal odd means a $1 bet returns $2.50 (including your stake). Fractional odds (common in the UK) show profit relative to stake — 3/2 means you profit $3 for every $2 staked.
All three formats express the same underlying probability; they just present it differently. Oddstatus lets you toggle between all three formats depending on your preference.
How to Convert Between Odds Formats
- American to Decimal
For positive American odds: Decimal = (American / 100) + 1. For negative: Decimal = (100 / |American|) + 1. Example: +200 → 3.0, -200 → 1.5.
- Decimal to American
If Decimal ≥ 2.0: American = (Decimal - 1) × 100. If 1 < Decimal < 2: American = -100 / (Decimal - 1). Example: 2.50 → +150, 1.67 → -150.
- Fractional to Decimal
Decimal = (Numerator / Denominator) + 1. Example: 3/2 → 2.50, 5/1 → 6.0.
- Calculate Implied Probability
Implied probability = 1 / Decimal odds. Example: Decimal 2.50 → 40% implied probability. This tells you how often the bookmaker expects this outcome to occur.
Understanding the Vig (Bookmaker Margin)
Sportsbooks build a margin (the "vig" or "juice") into their odds. If both sides of a two-way market are priced at -110, the implied probabilities sum to 104.76% — the extra 4.76% is the bookmaker's edge. Understanding vig helps you identify fair value: if a team's true probability is 55%, but the odds imply only 50%, you've found a positive expected value (+EV) bet.
Comparing odds across multiple sportsbooks is the simplest way to reduce the vig's impact on your returns. Even a few cents per bet compound significantly over hundreds of wagers.
Odds Format FAQ
Which odds format should I use?
Use whichever format you're most comfortable with. American odds are standard in the US, decimal in Europe/Australia, and fractional in the UK. Oddstatus supports all three with a single toggle.
What does +100 mean in American odds?
+100 means an even-money bet — you risk $100 to win $100. In decimal format this is 2.0, and in fractional format it's 1/1 (evens).
How do I calculate my potential payout?
For American odds: Positive odds payout = (stake × odds / 100). Negative odds payout = (stake × 100 / |odds|). For decimal: payout = stake × decimal odds. Remember that decimal includes your stake in the return.