Beta coefficients can be used to measure the systematic risk of the market as a whole relative to the volatility of an individual stock. A regression line's slope results from a regression of data points, and statistically speaking, that's what beta represents. A stock's return relative to the market is represented by each data point in finance. In order to calculate a security's beta, divide the covariance of its returns and the market's returns over a specific time period by the variance of the market's returns.