How to Read Betting Odds: American, Decimal, and Fractional Explained

American odds (-110, +150), decimal odds (1.91, 2.50), and fractional odds (10/11, 3/2) all express the same thing. Learn how to read and convert them.

01American Odds

American odds are the standard in the United States. They use positive and negative numbers centered around 100.

Negative odds (e.g., -150) show how much you need to bet to win $100. At -150, you bet $150 to win $100 (plus your $150 back).

Positive odds (e.g., +130) show how much you win on a $100 bet. At +130, you bet $100 to win $130 (plus your $100 back).

The bigger the negative number, the bigger the favorite. The bigger the positive number, the bigger the underdog.

02Decimal Odds

Decimal odds are common in Europe and Canada. They represent the total payout per unit bet, including your stake.

For example, decimal odds of 1.91 mean a $100 bet returns $191 total ($91 profit + $100 stake). Decimal odds of 2.50 mean a $100 bet returns $250 total ($150 profit).

To convert American to decimal: for negative odds, (100 / |odds|) + 1. For positive odds, (odds / 100) + 1. So -110 becomes 1.91, and +150 becomes 2.50.

03Fractional Odds

Fractional odds are traditional in the UK. They show profit relative to stake as a fraction.

For example, 10/11 means you win $10 for every $11 bet. 3/2 means you win $3 for every $2 bet ($150 profit on $100).

To convert to American: if the fraction is less than 1 (e.g., 10/11), it is negative: -(denominator / numerator * 100). If greater than 1 (e.g., 3/2), it is positive: (numerator / denominator * 100).

04Implied Probability

Odds imply a probability. To calculate it from American odds: for negative odds, |odds| / (|odds| + 100). For positive odds, 100 / (odds + 100).

So -110 implies 52.4% probability (110/210). +150 implies 40% probability (100/250).

The sum of implied probabilities for both sides always exceeds 100%. The excess is the vig, the sportsbook's edge. At -110 on both sides, the total implied probability is 104.8%, meaning the book has a 4.8% edge.

05Which Format Should You Use?

Use whatever format you are comfortable with. American odds are standard in the US and make it easy to see favorites vs underdogs at a glance. Decimal odds make it easy to calculate payouts. Fractional odds are traditional but less intuitive for many.

Most sportsbooks let you switch formats in settings. The key is understanding what the odds mean in terms of risk, reward, and implied probability, regardless of format.