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Interactive toolRuns in your browser

Theta Decay Visualizer

Visualise how an option's time value decays into expiry. Enter spot, strike, days and implied volatility to see the decay curve and per-day theta.

Quick answer: This visualiser plots an option's value against days-to-expiry using a Black-Scholes model, so you can see time decay accelerate as expiry approaches and read the approximate theta (value lost per day).

How to use it

Enter the spot, strike, days to expiry and implied volatility. The tool prices the option each day from now to expiry with a Black-Scholes model and draws the value curve, plus today's approximate one-day theta. Values are illustrative and exclude charges.

Frequently asked questions

What does the theta decay visualizer show?
It shows how an option's value falls as expiry approaches — the classic time-decay curve — and estimates theta, the value lost per day, for your chosen inputs.
Why does the decay curve steepen near expiry?
Because an at-the-money option's time value is roughly proportional to the square root of time left, so each remaining day removes a larger share of value as expiry nears — theta accelerates.
Is this the real price of my option?
No. It is a Black-Scholes model estimate for learning, using constant volatility and no charges. Live premiums differ due to skew, demand, spreads and STT.
How is theta calculated here?
As the difference between today's model value and the model value one day later, holding other inputs constant — a practical estimate of one day's time decay.

Runs entirely in your browser — no data leaves your device. Illustrative and educational only; exchange rules and charges apply in practice.

Educational tool only — not investment advice. Calculations are illustrative and use simplified models. See our Risk Disclosure.