Betting Odds Converter
Implied probability is the break-even win rate at this price — you need to win more often than this for the bet to profit long term.
How odds conversion works
Every odds format describes the same thing: how much a winning bet pays, and the probability the price implies. They just say it differently.
- American odds are anchored to $100. A favorite (-150) shows what you must stake to win $100; an underdog (+130) shows what $100 wins.
- Decimal odds show your total return per $1 staked, including your stake. 2.50 means $1 returns $2.50.
- Fractional odds show profit relative to stake. 3/2 means you win $3 for every $2 risked.
- Implied probability is 1 ÷ decimal odds — the break-even win rate at that price.
The number that actually matters for betting is the last one. If your own estimate of a team's chances is higher than the implied probability the book is charging, the bet has positive expected value. That gap between a fair price and the book's price is exactly what our true line measures.
Frequently asked questions
How do you convert American odds to decimal?
For positive American odds, divide by 100 and add 1 (so +150 becomes 2.50). For negative odds, divide 100 by the absolute value and add 1 (so -150 becomes 1.67).
What is implied probability?
Implied probability is the break-even win rate baked into a price. It equals 1 divided by the decimal odds. At -150 (decimal 1.67) the implied probability is about 60%, meaning you need to win more than 60% of the time to profit.
Why is the implied probability over 100% across both sides?
Because the sportsbook adds a margin called the vig. Add the implied probabilities of both sides and the total exceeds 100% — that overround is the book's built-in edge. Our no-vig calculator strips it out.