How violently does a stock move with the market? Enter covariance and variance — or correlation and volatilities — to get its beta and see how it's expected to react when the index rises or falls 10%.
Answer first: beta measures how much a stock moves relative to the overall market. A beta of 1 moves with the market; above 1 is more volatile; below 1 is calmer. This beta calculator computes it from covariance and variance, or from correlation and standard deviations — whichever data you have.
Beta = Covariance(asset, market) ÷ Variance(market) — or equivalently Correlation × (σ asset ÷ σ market).
Example: a covariance of 0.0030 against a market variance of 0.0025 gives a beta of 1.20. When the market rises 10%, this stock would be expected to rise about 12%; when the market falls 10%, it would fall about 12%.
Beta is the market-risk half of the famous Capital Asset Pricing Model. A high-beta stock (think speculative tech or small caps) amplifies the market's moves in both directions — exciting in a bull run, brutal in a crash. A low-beta stock (utilities, consumer staples) cushions the swings. Beta tells you how a holding behaves relative to the index, not whether it's a good investment.
Beta only captures systematic (market-wide) risk, not company-specific risk like a product recall or fraud. It's also backward-looking — calculated from past data that may not hold — and it's sensitive to the index and time window you measure against. A stock with low beta isn't "safe"; it just doesn't track the market closely. Use beta to understand how a position contributes to portfolio volatility, alongside the Sharpe ratio for the reward side.
Reality check: Beta is backward-looking, depends on the index and period chosen, and captures only market risk — not company-specific risk. A low beta is not the same as a safe investment. This is an educational calculator, not financial advice — verify your own numbers and see the U.S. SEC at investor.gov.
Pair it with the Sharpe ratio calculator, understand swings in what is market volatility, and review risk management basics.
Last updated 21 June 2026 · Written by Mustafa Bilgic. Educational only — not financial advice.
Beta measures how much a stock moves relative to the overall market. A beta of 1 moves with the market, above 1 means bigger swings than the market, and below 1 means smaller, more defensive moves. It captures market (systematic) risk.
Beta equals the covariance between the asset's returns and the market's returns, divided by the variance of the market's returns. Equivalently, it equals the correlation between them times the ratio of their standard deviations.
A beta of 1.2 means the stock tends to move about 20% more than the market. If the market rises 10%, the stock would be expected to rise roughly 12%; if the market falls 10%, it would fall about 12%. It amplifies moves in both directions.
Beta is backward-looking, depends on the index and time period used, and captures only market-wide risk, not company-specific risk. A low beta does not mean an investment is safe — only that it doesn't track the market closely.