How to Read American Odds

What +150 and -110 actually mean, how to convert them to decimal odds and win probability, and the formulas behind it.

American (moneyline) odds are the standard at US sportsbooks. Every price is a number that is either positive or negative, and the sign tells you which way to read it.

Negative odds: the favorite

A negative number is how much you must bet to win $100. At -150 you risk $150 to win $100. At -110 you risk $110 to win $100.

Positive odds: the underdog

A positive number is how much you win on a $100 bet. At +150 a $100 bet wins $150. At +300 it wins $300.

Converting to decimal odds

positive:  decimal = 1 + odds / 100     (+150 → 2.50)
negative:  decimal = 1 + 100 / |odds|   (-200 → 1.50)

Decimal odds are your total return per $1 staked, stake included — which is why every other calculation starts there.

Converting to implied probability

Implied probability is 1 divided by the decimal odds. It is the win chance the price needs to break even.

+150 → 2.50 decimal → 40.00%
+100 → 2.00 decimal → 50.00%
-110 → 1.91 decimal → 52.38%
-200 → 1.50 decimal → 66.67%

Why -110 isn't 50%

A fair coin flip would be +100 on both sides. At -110 you must win 52.38% of the time to break even, and the 2.38 extra points on each side are the sportsbook's margin — see what is vig.

Quick reminders

• American odds never fall between -100 and +100; even money is +100.
• Payout includes your stake; profit does not.