Options Probability Calculator
Estimate the probability that an option expires in the money, plus a quick estimate of probability of profit using your premium.
What this calculator does
This probability options calculator gives you a quick way to estimate outcomes for a single call or put at expiration. It uses a standard Black-Scholes-style framework to estimate:
- Probability the option expires in the money (ITM)
- Probability it expires out of the money (OTM)
- Approximate one-standard-deviation price range
- Estimated probability of finishing beyond your expiration break-even
Inputs explained
Option type
Choose Call if you benefit from upside, or Put if you benefit from downside.
Current stock price and strike price
These define how far in/out of the money the contract starts. A strike far from the current stock price usually has lower expiration probability, all else equal.
Days to expiration
More time generally increases the chance the stock can reach distant levels, but pricing and edge depend on premium and volatility.
Implied volatility (IV)
IV reflects the market’s expected annualized movement. Higher IV generally widens expected ranges and can increase the chance of touching a strike, but it also tends to raise option prices.
Risk-free rate
Included for completeness in the probability model. It usually has a smaller effect than stock price, strike, time, and volatility.
Premium paid
This is used to estimate a practical metric: probability of finishing above break-even (for calls) or below break-even (for puts) at expiration. That is usually more useful than ITM alone.
How to interpret the results
- ITM Probability: Chance the option has intrinsic value at expiration.
- OTM Probability: Chance it expires worthless.
- Break-even Probability: Chance expiration value exceeds your premium cost.
- 1σ Range: A rough 68% expected range by expiration under lognormal assumptions.
- Touch Estimate: A common shortcut approximation for touching strike before expiration.
Important limitations
Use this as an estimation tool, not certainty. Real trading outcomes can differ because:
- Volatility is not constant in real markets
- Price paths are not perfectly lognormal
- Earnings, macro events, and gaps can dominate model assumptions
- Early exercise, assignment risk, spreads, and liquidity are not modeled
- Risk-neutral probability is not the same as your personal forecast
Practical workflow for traders
- Start with strike and expiration that match your thesis timeline.
- Check ITM probability and break-even probability.
- Compare premium cost to expected move and scenario risk.
- Define max loss before entry (especially for long premium trades).
- Size small enough that a full premium loss is tolerable.
Bottom line
A good options decision is not just “Will this finish ITM?” It is: “Is the expected reward worth the premium and risk?” Use probability, pricing, and position sizing together for better decisions.