Theta Calculator for Options Time Decay
A simple educational tool for estimating how time decay may affect an options position when theta is known or estimated.
Estimate time decay
Enter option price, theta, days held, contracts, and position type to estimate the effect of theta over time.
Understand assumptions
The calculator uses simplified theta-based decay. It does not model changing volatility, price movement, assignment risk, liquidity, or full theoretical pricing.
Connect the concept
This site pairs with ThetaIndex.com, which can serve as the broader reference point for theta-related market concepts.
What the calculator is for
The calculator is meant for quick, plain-English exploration of theta exposure. It is especially useful when a trader already has a theta value from a brokerage platform or options chain and wants to estimate the dollar impact across a position.
Useful questions
- How much time decay might a long option lose over several days?
- How much theta exposure might a short premium position collect?
- How does contract count affect estimated dollar impact?
- How quickly does time decay become material relative to the option price?