Volatility measures the variability of an asset’s returns over time. Larger and less stable price changes generally mean higher volatility. It describes the size of fluctuations rather than whether the overall direction is upward or downward.
Historical and implied measures
Historical volatility is commonly calculated from the standard deviation of returns over a selected sample. The sampling interval, observation window and annualization convention affect the number. A 30-day measure should not be compared casually with one using a different method.
Implied volatility is derived from option prices through a pricing model. It reflects the volatility priced into those options, rather than an assurance about future realized movements. It also does not tell traders which direction the underlying asset will take.
Why traders monitor it
Volatility helps describe how widely prices may move around a position and informs position sizing, margin planning and option valuation. Thin liquidity, unexpected news and liquidations can amplify swings.
Low recent volatility does not rule out a sudden jump, and high volatility does not guarantee profitable opportunities. Two assets with the same historical measure can still have very different liquidity, downside risks and exposure to exceptional events.