Historical, implied and realised volatility: what is the difference?

Historical volatility is the spread of past daily returns, annualised. Realised volatility is the same kind of measure over the period you care about, so in practice the two words describe one idea with a different window. Implied volatility is the figure that makes an option's model price equal its market price, so it is read from prices people pay today, not from past closes.

The chart puts Nifty's at the money 30 day implied volatility and its 20 day realised volatility on one axis, from 1 Jul 2025 to 10 Jun 2026. The implied line sits above the realised line on about four in five of the sessions in the window. On those days the option market was pricing more movement than the trailing realised figure showed.

That gap is the raw material of what is called the variance risk premium: implied volatility tending to sit above the volatility that follows. This chart sets implied against trailing realised, so it only hints at it. It is an average tendency, not a daily fact. In the usual description, sellers collect the gap in small amounts on most days and give back large amounts on the few days the index jumps, which is why margin and loss limits matter to them.

The proper test compares today's implied volatility with the realised volatility over the following month, on the same horizon. The chart is a simpler view on the same dates, and it compares trailing realised with forward implied.

Keep the horizon and the window fixed when you compare two numbers. A longer realised window lags a fast change in the market, and a short one is noisy. The realised volatility module sets out the estimators on the same dated series.

Before you trade. Derivatives trading carries a high risk of loss. SEBI's study "Profitability of Individual Traders in the Equity Derivatives Segment (FY25 to FY26)" (August 2026) found that 87.7% of individual traders in equity F&O made net losses in FY26, with aggregate net losses of Rs 91,685 crore. Read the SEBI study