Beta Calculator
Compute a stock's beta from lists of stock and market returns to measure its volatility versus the market.
What this calculator does
The Beta Calculator estimates your result instantly from the values you enter, using standard investing & wealth formulas. Compute a stock's beta from lists of stock and market returns to measure its volatility versus the market. Calculations run in your browser, so nothing you type is sent to a server, and the output is an estimate for planning rather than financial advice.
Result
About Beta Calculator
The Beta Calculator measures how strongly a stock's returns move with the overall market. You enter two matching series of periodic returns — the stock's and the market's — and it computes beta as the covariance of the two series divided by the variance of the market series.
Beta is the standard gauge of systematic risk: a value of 1 moves in line with the market, above 1 amplifies market swings, and below 1 dampens them. Because the calculation uses only the paired return figures you supply, the result reflects your own data rather than any assumed market model.
Enter the stock returns and market returns as comma-separated percentages of equal length, press Calculate, and read the beta of the stock against the market.
Formula & Mathematical Calculation
Beta = Covariance(Stock Returns, Market Returns) ÷ Variance(Market Returns)
Calculation Example
For stock returns of 15, -5, 10, 20 against market returns of 10, -2, 8, 14, the covariance divided by the market variance gives a beta of 1.583 — the stock has amplified the market's moves.
Key Benefits
- Computes beta directly from your paired stock and market return series.
- Measures systematic risk relative to the market, the core input to CAPM.
- Requires equal-length series of at least two points, guarding the statistics.
- Uses only the returns you enter, so the beta reflects your own data set.
How to Use this Calculator
-
Enter the stock returns
Type the stock's periodic returns as comma-separated percentages in the Stock Returns field, for example 15, -5, 10, 20. -
Enter the market returns
Type the matching market returns as comma-separated percentages in the Market Returns field, for example 10, -2, 8, 14. -
Match the series length
Provide the same number of points in both fields — at least two — so each stock return pairs with a market return. -
Press Calculate
The tool divides the covariance of the two series by the variance of the market series to return the beta.
Assumptions & Limitations
What the calculation assumes
- Every value you enter is treated as an exact, known amount.
- Rates and contributions are assumed to stay constant for the whole period unless the form asks for them separately.
- Results use standard financial formulas and ignore fees, penalties and promotional terms that are not entered above.
- Inflation, tax changes and market volatility are not modelled unless a field for them is provided.
- Amounts are unit-agnostic: results are returned in the same currency you enter.
What it does not cover
- Beta Calculator produces estimates for education and planning, not a quote, offer or professional advice.
- Real-world outcomes differ when fees, taxes, rounding rules or provider-specific terms apply.
- Local regulations and tax rules vary by country and change over time; verify current rules for your jurisdiction.
- Figures are only as accurate as the inputs you supply — check them before acting on the result.
- For decisions with lasting financial impact, confirm the numbers with a qualified professional.
Frequently Asked Questions
Free to use, no account needed. Calculations run in your browser, so nothing you type is sent to a server. Results are estimates — how we build and check our calculators.
You May Also Need
Next step: browse the full Investing & Wealth calculators or read the related guides for context before you decide.