Implied Probability Calculator
Implied probability is the percentage chance a sportsbook is pricing into the odds. It includes the vig, so it overstates the true probability slightly. Use this to compare lines across books and to find positive expected value when your own estimate is lower than the implied number.
Result
How implied probability works
Implied probability translates odds into a percentage. For -150 (decimal 1.667), the implied
probability is 1 / 1.667 = 60%. The book is saying the favorite has roughly a 60%
chance to win, with the remaining vig built into the line.
Formulas
- From American positive (+X):
100 / (X + 100) × 100% - From American negative (-X):
|X| / (|X| + 100) × 100% - From decimal (D):
1 / D × 100%
How to use this
Compare your own estimate of the true win probability against the implied probability shown by the book. If your number is higher, the bet has positive expected value. The break-even win rate tells you how often you must hit at this price just to come out flat over the long run, ignoring taxes and bonuses.
Frequently Asked Questions
What does implied probability mean in sports betting?
Implied probability is the percentage chance the sportsbook is pricing into the odds. It includes the vig (book margin), so it overstates the true probability slightly. For example, -150 has 60% implied probability, but the no-vig true probability is closer to 57%.
How do I use implied probability to find value bets?
Compare your own estimated win probability against the book's implied probability. If your number is higher, the bet has positive expected value at that price. Combine with the no-vig calculator to strip vig and compare across books.
Why is implied probability not the same as true probability?
Sportsbooks build vig into both sides of a market. A -110/-110 spread shows 52.38% implied on each side, summing to 104.76%. The extra 4.76% is the vig. True (no-vig) probability is each side divided by the sum, which gives 50% on a symmetric line.
What's a break-even win rate?
The break-even win rate is the percentage of bets you must hit at this price just to come out flat over the long run, before taxes and bonuses. It equals the implied probability. At -110, you need to hit 52.38% to break even.
Does this calculator work for parlays and futures?
Yes. Implied probability works on any odds, regardless of bet type. Plug in a parlay's combined American or decimal odds and you get the implied probability the parlay hits.