Stock Beta Risk Calculator
Calculates a stock's beta to measure its price sensitivity relative to the broader market. Use it when assessing portfolio risk or comparing the volatility of individual stocks to a benchmark index.
Last updated: September 2026
Formula below · 2 sources (investor.gov, Wikipedia) · Updated Sep 2026
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About this calculator
Beta (β) measures how much a stock moves relative to the market. From volatility and correlation it is: β = ρ × (σ_stock / σ_market), where ρ is the correlation between the stock's and the market's returns and σ is each one's standard deviation of returns over the same period. This is mathematically identical to the regression definition β = Cov(stock, market) / Var(market), because Cov = ρ × σ_stock × σ_market. A beta of 1.0 means the stock moves in line with the market; above 1.0 means it amplifies market moves; below 1.0 means it moves less; a negative beta (negative correlation) means it tends to move against the market. Note that a volatile stock can still have a low beta if its correlation with the market is weak. The market return and risk-free rate are optional and do not change beta — they are only needed if you go on to estimate a CAPM expected return: Expected Return = Risk-Free Rate + β × (Market Return − Risk-Free Rate). Investors use beta to gauge systematic risk that cannot be diversified away.
How to use
Inputs: Stock Volatility = 20%, Market Volatility = 15%, Correlation = 0.7. Step 1 — Volatility ratio: 20 / 15 = 1.333. Step 2 — Beta: β = 0.7 × 1.333 = 0.93. Step 3 — Interpret: a beta of about 0.93 means the stock tends to move roughly 9.3% when the market moves 10%, even though it is more volatile than the market, because only 70% correlation links the two. Optional CAPM check: with a 10% market return and a 4% risk-free rate, the expected return is 4% + 0.93 × (10% − 4%) ≈ 9.6%. Always pair beta with context — sector, market cap, and the time period used to estimate the inputs all influence the result.
Frequently asked questions
What does a stock beta greater than 1 mean for investors?
A beta above 1.0 indicates the stock is more volatile than the overall market. For example, a beta of 1.5 implies that when the market rises 10%, the stock is expected to rise 15% — and fall 15% when the market drops 10%. High-beta stocks tend to be found in sectors like technology, biotechnology, and small-cap growth. They can amplify returns in bull markets but magnify losses in downturns, making them better suited for investors with a higher risk tolerance and longer time horizon.
How is beta used in the Capital Asset Pricing Model to estimate expected returns?
In CAPM, beta is the sole measure of systematic risk. The formula is: Expected Return = Risk-Free Rate + β × (Market Return − Risk-Free Rate). The term (Market Return − Risk-Free Rate) is the equity risk premium — the extra return investors demand for taking on market risk. Multiplying it by beta scales that premium to reflect the stock's specific level of market exposure. A stock with a beta of 0.5 would only require half the equity risk premium, while one with a beta of 2.0 demands twice as much. CAPM is widely taught but has limitations, as beta alone cannot capture all dimensions of investment risk.
Why does beta change over time and how should investors account for this?
Beta is estimated from historical price data, so it shifts as a company's business model, leverage, and market conditions evolve. A company that takes on significant debt will typically see its beta rise because fixed obligations amplify earnings volatility. Beta also varies with the time window and market index used for the calculation. Most analysts use a 2–5 year window with monthly returns as a reasonable balance between recency and statistical reliability. Because historical beta is an imperfect predictor of future beta, investors often use it directionally rather than as a precise forecast.