Estimate European Black-Scholes theta per calendar day.
It makes the prices, cash flows, rates, time periods, weights, and model conventions explicit so you can inspect an entered scenario without hidden live-market assumptions.
Calculation structure
Follow the stated model and units
Annual model theta combines diffusion, financing, and yield terms; displayed theta divides by 365.
Visual explanation
See how the inputs become the result
Market at expiryContract payoff
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Premium and costsNet outcome
Annual model theta combines diffusion, financing, and yield terms; displayed theta divides by 365.
Read the estimate correctly
Use the result within its boundaries
Enter code 1 for call or −1 for put and the shared Black-Scholes assumptions.
Displayed theta is per calendar day under continuous model time.
Quick guide
How to use this calculator
Enter the contract, market, expiry, rate, and position assumptions named by the fields.
Keep premiums, prices, multipliers, contract counts, and time conventions consistent.
Read the exact expiry-payoff or model assumptions before interpreting the result.
Calculation method
Calculation method
Annual model theta combines diffusion, financing, and yield terms; displayed theta divides by 365.
Expiry-payoff arithmetic uses the entered terminal underlying price. Model-derived values are explicitly estimates and reject unsupported domains.
Worked example
Worked example
Enter code 1 for call or −1 for put and the shared Black-Scholes assumptions.
Annual model theta combines diffusion, financing, and yield terms; displayed theta divides by 365.
Supported inputs
Precision and limits
Visible input limits
Fixed decimals accept up to 30 digits and 12 decimal places with absolute values capped at 1e12. General rates are bounded from −100% through 1000% where signed rates are meaningful.
No contract or market feed
No exchange specification, live quote, exercise style, dividend schedule, settlement rule, margin model, or contract multiplier is selected automatically.
Decision boundary
Outputs are entered scenarios, not quotes, forecasts, arbitrage findings, risk limits, suitability judgments, or recommendations.
Calculator-specific assumptions
Displayed theta is per calendar day under continuous model time.
