What is beta in stocks? How to read a stock's beta
Beta measures how strongly a stock tends to move with the overall market: 1 moves in line, above 1 amplifies market swings, below 1 dampens them.
What beta measures
Beta describes how sensitive an asset has been to movements in the broad market. The market itself has a beta of exactly 1. A stock with a beta of 1.3 has tended to rise about 30% more than the market on up days and fall about 30% more on down days; a stock with a beta of 0.6 has moved only about 60% as much.
Beta is the core of the capital asset pricing model (CAPM), which links an asset's expected return to its market risk: expected return = risk-free rate + β × (market return − risk-free rate). In practice it is mostly used as a quick gauge of how 'aggressive' or 'defensive' a holding is.
How beta is calculated
Beta comes from a regression of the asset's returns on the market's returns over the same periods:
β = Cov(Ra, Rm) ÷ Var(Rm) β = ρ × σa ÷ σm
Here ρ is the correlation between the two return series and σ their volatilities. The second form shows that beta mixes two things: how closely the asset follows the market (correlation) and how much bigger its swings are (relative volatility). The five-year beta on our stock pages comes from the data provider; the usual benchmark for US stocks is the S&P 500.
A worked example
Suppose a stock's correlation with the market is 0.8, its annual volatility is 30% and the market's is 16%. Its beta is 0.8 × 30 ÷ 16 = 1.5. If the market falls 10%, history suggests the stock falls about 15% on average — and rises about 15% when the market gains 10%.
Investors use this to shape a portfolio. Adding high-beta stocks such as fast-growing tech names makes it more sensitive to the market, while utilities, consumer staples and some healthcare companies have historically had betas below 1. A portfolio's beta is simply the weighted average of its holdings' betas.
Limitations and common mistakes
Beta is backward-looking and unstable: it changes with the period measured, the data frequency (daily versus monthly returns) and the benchmark chosen. A company that changes its business can have a very different beta in future.
Most importantly, beta measures only market-related risk. A gold miner or a biotech can have a low beta because it moves independently of the index — and still be extremely volatile. Check volatility, drawdown and how much of the stock's movement the market actually explains (R²) before calling a low-beta stock 'safe'.
Frequently asked questions
What is a good beta for a stock?
There is no good or bad beta, only one that fits your goals. Conservative investors often prefer betas below 1; investors who want more market exposure accept betas above 1, with the larger swings that come with them.
What does a negative beta mean?
That the asset has tended to move in the opposite direction to the market. True negative betas are rare among stocks; some hedging instruments and, at times, gold or government bonds have shown low or negative betas to equities.
Is beta the same as volatility?
No. Volatility measures how much an asset's price fluctuates on its own; beta measures how much of that movement is tied to the market. A stock can be very volatile yet have a low beta if its moves are unrelated to the index.