Beta Calculator

About this calculator

Beta (β) measures a stock's sensitivity to overall market moves, and it's a central input to the Capital Asset Pricing Model (CAPM) used across finance to estimate a stock's expected return and cost of equity. This calculator derives a simplified single-period beta directly from the stock's percentage change relative to the market's percentage change over the same period.

A beta of exactly 1 means the stock tends to move in lockstep with the market; beta above 1 means the stock amplifies market moves (more volatile, more risk and more potential reward), while beta below 1 means it dampens them (more defensive). Investors and portfolio managers use beta to gauge how much a stock adds to overall portfolio volatility and to size positions accordingly — note that professionally reported betas are usually computed via regression over many periods rather than a single pair of returns.