The metric that measures a stock’s volatility relative to the market is beta.
Beta measures how strongly a stock’s returns have moved in relation to a chosen market benchmark. A beta of 1 suggests movement broadly in line with the benchmark; a beta above 1 indicates greater sensitivity, while a beta below 1 indicates lower sensitivity. A negative beta implies that the asset has tended to move in the opposite direction.
For example, a stock with a beta of 1.5 has historically tended to move about 1.5% when its benchmark moved 1%, though beta is an estimate rather than a promise. The result depends on the time period, data frequency, and benchmark used—often the S&P 500 for US stocks.
Beta is not the same as total volatility. Standard deviation measures the overall dispersion of a stock’s returns, including company-specific risk. Beta focuses on systematic, market-related risk. R-squared indicates how much movement is explained by the benchmark, while alpha measures performance relative to a model’s expectation.