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Stock Beta Calculator

Measure how strongly a stock or fund moves with the market. Paste prices or returns for the stock and a benchmark index, and get beta, alpha, correlation and R-squared, with a scatter plot, regression line and every matched return.

Last updated: October 24, 2026

Your data

Stock name

Benchmark name

Stock prices or returns

Market prices or returns

One value per line. If both lists have dates, rows are matched by date; otherwise they are matched by position from the most recent value. Or paste two columns (stock, market) into the first box and leave the second empty.

Values are

Frequency

Chart

How it was calculated

Matched returns

How to use the Stock Beta Calculator

Paste the stock's prices in the first box and the benchmark's prices (for example a broad market index) in the second, ideally with dates.
Check "Values are": Auto treats positive lists as prices and lists with negatives or % signs as returns.
Pick the frequency or leave it on Auto to detect daily, weekly or monthly data from the dates.
Read beta, correlation and R-squared and the plain-English interpretation.
Inspect the scatter chart: the slope of the orange regression line is beta. Download the CSV if you need the detail.

The beta formula

Beta: β = Cov(R_s, R_m) ÷ Var(R_m) = Σ(R_s − R̄_s)(R_m − R̄_m) ÷ Σ(R_m − R̄_m)²
Same thing, another way: β = r × σ_s ÷ σ_m
Alpha (intercept): α = R̄_s − β × R̄_m
R-squared = r², the share of variance explained by the market
Standard error of beta = √( Σe² ÷ (n − 2) ÷ Σ(R_m − R̄_m)² ), where e are the regression residuals

When you paste prices, each series is first turned into simple period returns, R = P_t ÷ P_t−1 − 1, using only the dates both series share.

How to read beta

Beta	Meaning	If the market rises 10%, the stock tends to…
Below 0	Moves against the market	Fall
0	No linear relation to the market	Show no consistent reaction
0.5	Defensive	Rise about 5%
1.0	Moves with the market	Rise about 10%
1.5	Aggressive	Rise about 15%
2.0	Highly aggressive	Rise about 20%

These are average tendencies. With a low R-squared, individual periods can differ a lot from what beta suggests.

Tips

Choose a fitting benchmark. Measure a US large-cap stock against a broad US index, a small-cap stock against a small-cap index, and so on.
Portfolio beta is the value-weighted average of the holdings' betas: a portfolio that is 60% in a 1.2-beta fund and 40% in a 0.7-beta fund has a beta of 0.6 × 1.2 + 0.4 × 0.7 = 1.0.
Beta only captures market risk. Look at volatility for total risk and maximum drawdown for the worst loss.

Frequently asked questions

What is beta?

Beta measures how much a stock's returns move with the market. A beta of 1 means it moved one for one with the benchmark on average, 1.5 means about 1.5% for each 1% market move, 0.5 means about half as much, and a negative beta means it tended to move the opposite way.

How is beta calculated?

Beta = Cov(Rs, Rm) ÷ Var(Rm), where Rs are the stock's period returns and Rm the market's returns over the same periods. It is identical to the slope of a least-squares regression line of stock returns on market returns, which is what the scatter chart shows.

What data should I use to calculate beta?

A common convention is 60 monthly returns (5 years) against a broad index such as the S&P 500; many data providers instead use 2 years of weekly returns or 1 year of daily returns. Different choices give different betas, so compare stocks using the same period, frequency and benchmark. Use adjusted closing prices so dividends and splits do not distort returns.

What is the difference between beta, correlation and R-squared?

Correlation (r) measures how consistently the two move together, from −1 to 1. R-squared is r², the share of the stock's return variation explained by the market. Beta combines correlation with relative volatility: β = r × (σ stock ÷ σ market). A stock can have a high beta but low R-squared if it is very volatile but only loosely tied to the market.

What is adjusted beta?

Adjusted beta (the Blume adjustment) is 0.67 × raw beta + 0.33 × 1. It pulls the historical beta toward 1 because betas tend to drift toward the market average over time, and it is commonly shown by financial data terminals.

What does alpha mean here?

Alpha is the intercept of the regression: the average return of the stock per period that is not explained by the market. It is shown per period and roughly annualized. It ignores the risk-free rate, so treat it as an indication, not a formal Jensen's alpha.

Why is my beta different from the one on a finance website?

Published betas depend on the benchmark, the time window, the return frequency, whether prices are adjusted for dividends, and whether an adjustment is applied. Change any of these and the number moves. Short or volatile periods can shift beta noticeably, so check the 95% range shown.

Are all the tools on FreeToolCabin tested for quality and accuracy?

Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.

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