Why this tool exists

Most free options tools show you the payoff diagram and stop there. They tell you what happens, not why.

This playground was built as a learning tool for retail options traders who are past the beginner stage — you know what a call is, you've done a few wheels, and you're tired of “trading by vibes.” The differentiator is P&L Decomposition: for any scenario you can imagine, the tool breaks your P&L into Δ / Γ / Θ / Vega dollar contributions with the exact formula that produced each number.

The tool is educational only. It does not execute trades, hold positions, or provide recommendations. It uses public 15-minute-delayed market data from yfinance.

Methodology

All prices and Greeks are computed with the Black-Scholes model for European-style exercise, with no dividend adjustment, a flat risk-free rate (user-set, default 5%), and calendar-day/365 time. Each leg is priced at its own implied volatility when one is set (or fetched from the chain); otherwise the position-level IV applies. Real US options are mostly American-style — for calls on non-dividend payers the difference is negligible, but deep-ITM puts and options around ex-dividend dates can diverge meaningfullyfrom these model values. Market data is 15-minute-delayed via yfinance. The P&L decomposition uses first-order Greeks plus ½Γ·dS²; the residual line shows what the approximation misses. Educational only — not an execution or pricing service.

Credits

Built by Sumbul Amin with Claude — a working example of an AI-assisted product build from spec to production. Backend in Python (FastAPI), frontend in Next.js + TypeScript, deployed on Railway and Vercel.

Not trading advice

Everything here is an educational simulation. It doesn't know your portfolio, risk tolerance, or financial situation. Any real trading decision is yours alone. Past model performance — including the walkthrough numbers used to validate the math — is not predictive of future results.

Feedback

Found a bug? Have a strategy you'd like modeled? Want a new educational article in Learn? The best way to make this better is to tell me what confused you. Feedback goes directly into the backlog.