Introductory Context
"Historical Volatility (HV) is the annualised standard deviation of actual past returns — measuring how much the underlying has actually moved. IV is the market's expectation of future volatility. When IV significantly exceeds HV, options may be overpriced (good selling environment). When IV is below HV, options may be underpriced (good buying environment). "
What Historical Volatility Measures
Historical Volatility (HV) is calculated from the actual daily returns of the underlying over a specified lookback period. The typical periods used in options analysis:
• Calculated from the past 10 trading days. Reflects the most recent short-term volatility. Responsive to recent market events: 10-day HV (HV10).
• Calculated from the past 20 trading days (approximately 1 month). The most commonly referenced HV for monthly options analysis: 20-day HV (HV20).
• Comparable to the 30-day period implied by India VIX. The most direct comparison point for assessing IV vs HV: 30-day HV (HV30).
• Mdium-term historical context. Smooths out short-term spikes: 60-day HV (HV60).
• Full-year historical volatility. Long-term structural volatility of the underlying: 252-day HV (HV252).
The calculation for each period: take the natural log of each day's close divided by the previous day's close (daily log return). Calculate the standard deviation of these daily log returns. Multiply by √252 (the square root of 252 trading days in a year) to annualise. The result is historical volatility expressed as an annualised percentage.
HV Calculation — The Practical Shortcut
You do not need to calculate HV manually. TradingView displays historical volatility on any chart with the 'Historical Volatility' indicator. Sensibull shows current IV alongside historical volatility for context. The NSE options chain provides IV column data which, compared against the historical HV of the underlying, gives you the IV-HV comparison immediately.
What HV Tells You About the Underlying
Historical Volatility tells you the actual magnitude of recent price movements in the underlying, expressed as an annualised percentage. For Nifty 50:
• Unusually quiet period — Nifty has been moving very little. Historically rare. HV below 10%
• Normal quiet range — moderate daily moves, steady market. HV 10–15%
• Normal active range — the typical environment for Indian equity markets. HV 15–20%
• Elevated volatility — significant market events or sustained directional moves. HV 20–30%
• Crisis-level volatility — major events like COVID March 2020, GFC 2008. HV above 30%
These reference ranges provide context when you see India VIX or any options' IV level. An IV of 18% is slightly elevated in a market where HV20 is 12% (options pricing in more volatility than has been realised). The same IV of 18% is actually below realised volatility if HV20 is 22% (options are cheap relative to what has been happening).
The IV vs HV Comparison — The Key Signal
The most powerful use of Historical Volatility: comparing it to Implied Volatility to assess whether options are currently priced too high or too low relative to recent realised movements.
IV > HV — Potentially Overpriced Options
When implied volatility (India VIX or specific option IV) significantly exceeds historical volatility, the market is pricing in more future volatility than has actually occurred recently. This can happen for legitimate reasons — an upcoming event (Budget, RBI, elections) that genuinely warrants elevated uncertainty. Or it can reflect excess fear or speculation that will normalise after the event resolves.
IV > HV environment: consider option selling strategies (collecting premium that is high relative to realised volatility) or spreads that reduce net vega exposure (buying less time value while still expressing a directional view).
IV < HV — Potentially Underpriced Options
When implied volatility is below historical volatility, options are cheap relative to what the market has actually been doing. In this environment, option buyers are paying less in premium than what the underlying's actual movement would justify. This creates structural tailwind for buyers — they are likely getting more actual price movement than the options are pricing.
IV < HV environment: generally favourable for option buying. The market's actual realised volatility may well exceed what the options are pricing, making premium payments relatively cheap.
Correlation Is Not Causation
IV > HV does not guarantee that selling options will be profitable — the next period of volatility may be higher than the past period that HV measures. IV < HV does not guarantee that buying options will be profitable — the underlying may suddenly become quieter. HV provides historical context, not a crystal ball. Used as one signal in a multi-factor analysis alongside IV rank, PCR, and technical levels, it adds value. Used in isolation as a trading rule, it can mislead.