Implied Volatility and Historical Volatility
IV is inferred from an option price using a model. It is annualized and varies across strikes and expirations. A higher IV increases a vanilla option model value with other inputs held constant; it does not establish that the market price is wrong. Historical volatility describes past returns and is not a forecast.
Read the Sample Before the Signal
- Enter a supported ticker and press Analyze IV. Loading a new ticker clears the previous result; changing the draft alone does not relabel loaded data.
- Check the loaded ticker and returned contract count. The request covers strikes within 10% of a separately fetched spot and stops at 250 records. Expiry and type filters narrow that sample, not a complete market chain.
- Read the nearest-expiry sampled IV alongside 20-return HV. The IV reference uses the nearest returned strike at the earliest returned future expiry; call and put IVs at that strike are averaged when both exist.
- Select a contract for the model adjustment. A change of +5 percentage points means 20% becomes 25%, not 21%. Inspect the fixed rate, dividend and time conventions beside the model.
What This Comparison Can Establish
The historical chart uses sample standard deviation of 20 daily log close returns multiplied by the square root of 252. Returned closing-price adjustments and gaps affect the calculation. The current IV line is a reference across the chart, not fabricated IV history. No IV percentile or IV rank is calculated without an actual comparable historical IV series.
IV minus HV is a difference in percentage points. Their horizons can differ, so the spread alone does not identify cheap or expensive options. Neither an IV level nor a term-structure shape establishes a trading edge.
Compare Expirations with Care
The term table compares the nearest available strike at each sampled expiry. A missing call or put stays unavailable. Annualized IV can slope upward, downward or form a hump; more time does not mechanically imply higher annualized volatility. Event exposure, strike differences and missing contracts can affect the shape. Expiry-day contracts are excluded because this page has no exchange settlement-time model.
Model Changes Are Not Trade Profit
The adjustment panel keeps spot, strike, remaining time, a fixed illustrative rate and zero dividend yield constant while changing IV. European Black–Scholes does not model early exercise, discrete dividends, spreads, commissions or actual fills. The chart subtracts the original model value from each scenario per share; it is not an expiration payoff or realized P&L. A zero IV adjustment must produce zero modeled price change.
Vega is a local sensitivity per one percentage-point change in IV. Large changes require repricing and are not accurately described by multiplying one fixed vega. A drop after earnings can reduce a long option model value with other inputs fixed, but the stock move and time decay also matter. No fixed 30–50% drop is assumed.
Sources and Data Limits
Massive snapshot documentation explains pagination, optional IV/Greeks and plan-dependent delay. OIC technical information distinguishes historical and implied volatility. Cboe analytics FAQs explains model inputs and missing IV. Retrieval time on this page is not an exchange quote timestamp. This educational comparison is not an order or a recommendation.