American Betting Odds Explained

American betting odds, also known as moneyline odds, are the default format used by sportsbooks in the United States. Unlike decimal or fractional formats, they show at a glance how much you need to risk or how much you stand to win. Understanding this format is essential for anyone analysing betting markets, comparing offers, or building a strategy in the U.S. market.

What Do +100 and -150 Actually Mean?

At the core of the American odds system is a simple idea: how much you need to stake to win $100—or how much you can win from a $100 bet. The sign in front of the number is crucial.

• Negative odds (e.g. -150) represent the favorite. A bet of $150 returns $100 profit, meaning the total return is $250.

• Positive odds (e.g. +200) indicate the underdog. A $100 stake returns $200 profit—$300 in total.

How to Convert American Odds to Decimal or Fractional Formats

While U.S. sportsbooks rely on American odds, many international platforms use decimal or fractional formats. Understanding the conversion allows bettors to assess value across jurisdictions.

• For positive American odds: divide the number by 100 and add 1.
  Example: +150 → 1.50 + 1 = 2.50

• For negative American odds: divide 100 by the absolute value, then add 1.
  Example: -200 → (100 ÷ 200) + 1 = 1.50

Fractional conversions follow similar logic. +150 becomes 3/2, -200 converts to 1/2.

These conversions aren’t just academic. They let you compare pricing at a glance. If a U.S. sportsbook is offering +110 and a European site has 2.00, you instantly know which line is better.

Understanding Implied Probability

Every betting odd contains a hidden message: the bookmaker’s implied probability of an event. Decoding that message is key to evaluating whether a bet offers value.

To calculate implied probability:

• For positive odds:
  100 / (odds + 100)

• For negative odds:
  odds / (odds + 100)

So:

• +200 implies a 33.3% chance of winning

• -150 reflects a 60% chance

This allows you to compare the bookmaker’s expectations with your own research. If you believe an outcome is more likely than the odds suggest, you may be looking at a +EV (positive expected value) opportunity.

Using American Odds in Betting Strategies

The structure of moneyline odds offers several tactical advantages—provided you understand how to use them.

Risk Management

Negative odds expose you to greater liability. Betting $300 to win $200 may sound safer, but it’s a larger financial commitment. On the other hand, longshots at +300 require smaller stakes, but the probability of winning is low. Knowing how to balance your position relative to both the odds and the real-world matchup is key to protecting your bankroll.

Spotting Value in the Market

A strong understanding of implied probabilities allows bettors to pinpoint overpriced or underpriced lines. If a team is priced at +150, and you believe they have closer to a 50% chance of winning, that’s a gap worth exploring.

Line Shopping and Market Comparison

Moneyline odds also make it easier to scan the market. A shift from -120 to -110 may not seem dramatic, but it materially improves your return over time. Serious bettors regularly compare odds across multiple sportsbooks to ensure they’re consistently on the right side of price movement.