Beta

Stock trading dictionary: meaning, example and how traders use it.

Last updated: October 17, 2026

Definition: Beta is a measure of how sensitive a stock's returns are to movements in the overall market. A beta of 1 means the stock tends to move in line with the market; above 1 means more volatile, and below 1 means less.

How beta works

Beta compares a security's price movements with a benchmark index, usually the S&P 500 for US stocks. It captures systematic risk: the portion of volatility tied to broad market swings that diversification cannot remove.

  • Beta = 1: moves roughly in step with the market.
  • Beta greater than 1: tends to amplify market moves. Many growth and technology stocks fall here.
  • Beta between 0 and 1: tends to move less than the market, common among utilities and consumer staples, often found among blue-chip stocks.
  • Negative beta: tends to move opposite the market, which is rare among stocks.

Beta formula

Beta = Covariance(stock returns, market returns) / Variance(market returns)

In practice, beta is estimated by regressing a stock's periodic returns, often five years of monthly data, on the market's returns. The slope of that line is beta. Different data providers use different periods and benchmarks, so published betas for the same stock can vary.

Example: interpreting beta

Suppose a hypothetical stock has a beta of 1.4. If the market rises 10%, the stock would be expected, on average, to rise about 14%. If the market falls 10%, it would be expected to fall about 14%. A stock with a beta of 0.6 would be expected to move about 6% in either direction.

Now suppose an investor holds a portfolio that is 50% in the 1.4-beta stock and 50% in the 0.6-beta stock. The portfolio's beta is the weighted average: (0.5 x 1.4) + (0.5 x 0.6) = 1.0. Beta also feeds the calculation of alpha, which measures return above what beta would predict.

Beta can also be estimated for funds, sectors, and other assets using the same approach. Short-term traders sometimes calculate it on daily or weekly returns over a shorter window to capture how a stock is behaving recently, while long-term investors prefer longer windows that smooth out temporary swings. Neither approach is right or wrong; each answers a slightly different question about risk.

How investors use beta

Investors use beta to set the market risk of a portfolio. Someone who expects a bull market may tilt toward higher-beta stocks, while a cautious investor may favor low-beta holdings ahead of a possible bear market. Beta is also used to size hedges with index futures or ETFs.

Limitations of beta

Beta is backward-looking and can change as a company's business evolves. It measures only market-related risk, not company-specific risks such as a failed product or lawsuit. A low beta does not mean low volatility: a stock can swing wildly for its own reasons while correlating weakly with the market. Results also depend on the period and index used.

Frequently asked questions

Is a high beta good or bad?

Neither by itself. A high beta means greater sensitivity to market moves, which can magnify gains in rising markets and losses in falling ones; whether it fits depends on your risk tolerance.

What does a beta of 1.5 mean?

It means the stock has historically moved about 1.5 times as much as the market, rising roughly 15% when the market rises 10% and falling similarly when it falls.

What is the difference between beta and volatility?

Volatility measures how much a stock's price swings overall, while beta measures how much of that movement is tied to the market's movements.

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For information only, not investment advice. See the disclaimer.