Implied Probability Calculator
Every price implies a win probability. Enter one side's odds to see it. Add the other side's odds and the calculator also takes out the book's margin, the vig, and shows the fair price for both sides.
The formula
Implied probability = 1 ÷ decimal odds
- Minus odds: odds ÷ (odds + 100). At -150: 150 ÷ 250 = 60%.
- Plus odds: 100 ÷ (odds + 100). At +130: 100 ÷ 230 = 43.5%.
Finding the vig and the fair odds
Add both sides' implied probabilities. On a fair market they would sum to exactly 100%; the amount over 100% is the book's margin. Divide each side by the total to get its fair, no-vig probability.
Example: -150 / +13060.0% + 43.5% = 103.5%, so the margin is about 3.5%.
Fair probabilities: 60.0 ÷ 103.5 = 58.0% and 43.5 ÷ 103.5 = 42.0%, or about -138 and +138.
Fair probabilities: 60.0 ÷ 103.5 = 58.0% and 43.5 ÷ 103.5 = 42.0%, or about -138 and +138.
Example: -110 / -11052.4% + 52.4% = 104.8%. Each side is really 50%, a fair price of +100,
which is why -110 needs a 52.4% win rate to break even.
The fair probability is the number to beat. A bet is worth making only when you think it wins more often than that; see +EV betting.
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