BasicsGuide 01 of 05
How to Read Betting Odds
American, decimal, and fractional prices, and what the number is actually saying about implied probability.
OddsListing education desk
Updated · 7 min read
On this page4 sections
American odds
The number with a plus or minus is the U.S. default. −150 means you risk $150 to win $100. +130 means you risk $100 to win $130. Negative is the favorite; positive is the underdog. The larger the absolute value on the minus side, the heavier the favorite.
Implied probability
For a favorite: probability = risk / (risk + win). −150 is 150 / 250 = 60%. For an underdog: probability = 100 / (odds + 100). +130 is 100 / 230 ≈ 43.5%. Add both sides of a two-way market and you get more than 100%. That overround is the juice. The gap between those two percentages is what the book is charging you to play.
Decimal and fractional
Decimal odds are the total return per $1 staked, stake included. 2.50 means $1 becomes $2.50. Fractional 5/2 is the profit per unit staked. Convert American to decimal: favorite is 1 + 100/|odds|; underdog is 1 + odds/100. We quote American on OddsListing because that is the board U.S. players actually see.
Worked example
Pick a side on the sample two-way below. The desk converts American to decimal, implied probability, and what a ticket returns. These are teaching prices, not a live number — confirm the board on the book before you bet.
Worked example
Cowboys at Dolphins
Sample prices. Confirm the live number on the book.
- Pick
- Cowboys
- Profit
- $67
- Return
- $167
- Market hold
- 3.5%
Education, not a wagering instruction. Confirm every number on the sportsbook. 21+.
