American Odds Explained: How They Compare to Decimal & Fractional Odds
- WinFact
- May 1
- 2 min read
Learn the difference between U.S., European, and UK odds formats with simple examples and calculations.

Table of Contents
What Are American Odds?
How to Read and Interpret American Odds
How to Convert American Odds to Probability
American vs Decimal Odds
American vs Fractional Odds
Real-World Examples
Summary / Takeaways
Introduction
There are three major ways to display betting odds: American, decimal, and fractional. Understanding these formats isn’t just trivia—it affects how you calculate risk, payout, and betting value. If you're betting in the U.S., you'll mostly see American odds. But if you're reading European websites or watching UK sportsbooks, expect decimal or fractional. Let’s break it all down.
What Are American Odds?
American odds (also called “moneyline odds”) are based around winning or risking $100. They come in two types:
Positive odds (+) show how much profit you'd make on a $100 bet.
Negative odds (–) show how much you'd need to bet to win $100.
Example:
+200 = You bet $100, win $200 profit
-150 = You bet $150 to win $100 profit
How to Read and Interpret American Odds
Here’s how to spot the difference between a favorite and an underdog:
Odds | Type | Meaning |
-200 | Favorite | You need to bet $200 to win $100 |
+150 | Underdog | You win $150 from a $100 bet |
Why It Matters:
Favorites are more likely to win, but pay less.
Underdogs are riskier, but reward more.
How to Convert American Odds to Probability
To understand value, convert odds into implied probability. Here's how:
For positive odds (+X):
Probability % = 100 / (odds + 100) × 100
Example: +200= 100 / (200 + 100) × 100 = 33.3%
For negative odds (–X):
Probability % = odds / (odds + 100) × 100
Example: -150= 150 / (150 + 100) × 100 = 60%
American vs Decimal Odds
Bet Type | American | Decimal | Profit on $100 Bet |
Favorite | -150 | 1.67 | $66.67 |
Even | +100 | 2.00 | $100 |
Underdog | +200 | 3.00 | $200 |
Decimal Formula:Decimal = (American odds / 100) + 1 (for positive)Decimal = 100 / abs(American) + 1 (for negative)
American vs Fractional Odds
Bet Type | American | Fractional | Meaning |
Favorite | -150 | 2/3 | Bet $3 to win $2 |
Even | +100 | 1/1 (Evens) | Bet $1 to win $1 |
Underdog | +200 | 2/1 | Bet $1 to win $2 |
Fractional odds are common in the UK. They're written like "5/1" or "1/2" and show profit relative to your stake.
Real-World Examples
Example 1: NFL Game
Patriots -200 vs Jets +170
Patriots = Favorite → You must bet $200 to win $100
Jets = Underdog → Bet $100 to win $170
Example 2: UFC Fight
Fighter A: +135, Fighter B: -165
Bet $100 on Fighter A = $135 profit
Bet $165 on Fighter B = $100 profit
Summary / Takeaways
American odds use + and – to show underdogs and favorites.
+150 means $100 wins you $150.
-150 means you need $150 to win $100.
Decimal odds are easier for calculations (common in Europe).
Fractional odds are popular in the UK and betting shops.
You can convert odds to implied probability to find value.
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