Three Ways to Read the Same Number
Sports betting odds communicate two things: the probability of an outcome and the payout if you're right. The confusion is that there are three different ways to express the same information, and different parts of the world (and different sportsbooks) use different formats.
Once you understand all three, you can convert between them instantly.
American Odds (Moneyline Format)
American odds are what you'll see on US sportsbooks. They're expressed as either a positive or negative number.
Negative odds (e.g., -150): The favorite. You must bet $150 to win $100.
Positive odds (e.g., +130): The underdog. A $100 bet wins $130.
The break-even formulas:
- Negative: (|odds| / (|odds| + 100)) × 100 = implied probability
- Positive: (100 / (odds + 100)) × 100 = implied probability
At -150: 150/250 = 60% implied probability At +130: 100/230 = 43.5% implied probability
Decimal Odds (European Format)
Decimal odds are used on most international betting exchanges and are arguably more intuitive. They represent your total return per $1 wagered, including your stake.
Example: Decimal odds of 2.50 mean a $100 bet returns $250 total ($150 profit + $100 stake).
Conversion from American:
- Positive odds: (American + 100) / 100
- Negative odds: (100 / |American|) + 1
-150 American → 100/150 + 1 = 1.667 decimal +130 American → (130 + 100) / 100 = 2.30 decimal
Fractional Odds (British Format)
Fractional odds (3/1, 5/2, etc.) show profit relative to stake. 3/1 means you win 3 units for every 1 unit wagered.
Conversion to decimal: Numerator/denominator + 1 3/1 = 3 + 1 = 4.00 decimal 5/2 = 2.5 + 1 = 3.50 decimal
Fractional odds aren't common on US sportsbooks but appear in horse racing.
Why This Matters for Your Betting
Converting to implied probability and comparing it to your own probability estimate is the core skill of value betting. Once you can read all three formats and convert to probability, you can evaluate any bet in any market.
Oddible displays your bets in standard American format but can help you calculate expected value across any odds format.
[Calculate EV and track results with Oddible →]
