Historical Volatility
Historical volatility (HV) measures the actual price fluctuations of an underlying asset over a defined past period, typically calculated as the annualised standard deviation of daily log returns. It is used alongside implied volatility to assess whether current option premiums are elevated or suppressed relative to realised market movement.
Historical volatility is a backward-looking measure. It quantifies how much the underlying actually moved over a chosen lookback window — commonly 10, 20, or 30 trading days. Unlike implied volatility, which is derived from option prices and reflects market expectations, HV is derived directly from price data and is entirely factual.
For Nifty 50, 20-day historical volatility has historically ranged from approximately 8–10% during calm, trending markets to well above 30% during severe stress events such as the March 2020 COVID-19 sell-off or the global financial crisis. Comparing the current implied volatility of Nifty options to the 20-day HV helped traders assess whether the market was overpaying or underpaying for options relative to the recently realised level of price movement.
When IV exceeds HV significantly, option premiums are relatively expensive — the market is pricing in more volatility than has recently been realised. This has historically been a more favourable environment for premium sellers. When HV exceeds IV, premiums are relatively cheap relative to realised movement, which has historically been a more favourable environment for premium buyers. This IV–HV comparison is a useful heuristic but not a guarantee of future outcomes.
A misconception is that historical volatility predicts future volatility. HV describes what happened in the past; it does not reliably forecast what will happen going forward. Volatility clustering — where high-volatility periods tend to follow high-volatility periods — has been observed in Indian markets, but regime changes can cause HV to shift dramatically without warning.
Different lookback windows produce different HV figures, and the choice of window introduces subjectivity. A 10-day HV captures very recent price behaviour and is highly responsive to sudden moves. A 252-day HV provides a long-run average but smooths out recent spikes. Practitioners often monitor multiple windows simultaneously to get a fuller picture of the volatility regime.