Options Theta Calculator
Estimate the daily theta of European options: how much time value decays each day.
Results
Fill in the inputs and click Calculate.
- Theta (daily)
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Risk disclaimer
This calculator provides theoretical references, not investment advice. Real markets include supply/demand, vol surfaces and liquidity; Greeks change in real time.
What does it measure?
Theta is usually negative — options lose value as time passes. Buyers pay time cost while sellers earn it; use it to gauge holding cost.
How to use
- Choose call or put.
- Enter spot, strike, time to expiry in years and annual volatility %.
- Risk-free rate defaults to 0; fill it in if needed.
- Click Calculate to see this Greek.
Formula (Black-Scholes)
- Theta (daily) = annualized theta ÷ 365
Example
Spot 100, strike 100, 1 year, vol 20%, rate 0%: daily theta ≈ −0.0109 for call and put.
FAQ
How should I read these values?
Each is a model-based partial derivative of option price: Delta w.r.t. spot, Gamma w.r.t. delta, Vega w.r.t. volatility, Theta w.r.t. time.
Why is the risk-free rate 0 by default?
Crypto options are often priced with a near-zero risk-free rate; change it for classic-market comparisons.