Implied Probability Calculator
Convert option delta or probability to implied odds
Report a Problem
Found a bug or have a suggestion? Help us improve this tool.
What is this tool?
The Implied Probability Calculator converts between options delta and probability of expiring in-the-money, or between betting odds (American, decimal, or fractional) and implied probability. It also calculates breakeven prices for options and shows the bookmaker overround when analyzing betting odds.
How to use
- 1
Choose mode
Select Delta mode (options) or Odds mode (betting).
- 2
Enter parameters
In Delta mode: input delta, strike, and spot price. In Odds mode: input odds in your preferred format.
- 3
View probability
See the implied probability percentage, breakeven price (options), or overround (betting odds).
Frequently Asked Questions
What does delta tell me about probability?
Delta approximates the probability of an option expiring in-the-money. A 0.30 delta call has roughly a 30% chance of finishing ITM. This is an approximation—actual probability also depends on implied volatility and time decay.
What is overround?
Overround is the bookmaker's built-in profit margin. If implied probabilities across all outcomes sum to 105%, the overround is 5%. Lower overround means better value for bettors.
How do I convert American odds?
For positive American odds (e.g., +200): probability = 100 / (odds + 100) = 33.3%. For negative odds (e.g., -150): probability = |odds| / (|odds| + 100) = 60%.