Jensen’s Alpha Calculator

Written by Great Medico

Updated September 25, 2026 •2 min read

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Jensen’s Alpha Calculator is most useful as a scenario tool: change one assumption at a time and watch how the modeled return, value, rate, or risk measure responds.

What this calculator does

Jensen’s Alpha Calculator calculates Jensen’s alpha by comparing the portfolio return with the CAPM-implied return based on the risk-free rate, benchmark return, and portfolio beta. It uses only the information collected by this interface; costs, taxes, rates, market data, or operating assumptions that are not shown are not silently added to the result.

How to use it

Enter Portfolio return (%), Market/benchmark return (%), Risk-free rate (%), Portfolio volatility (%), Downside deviation (%), and Portfolio beta. Keep percentage assumptions in the units shown on the form and make sure the time unit of rates matches the term or period count. Before using the result in a decision, recheck unusually large or negative values against the source data rather than assuming the calculator is correcting an inconsistent input.

How the calculation works

Jensen’s alpha = portfolio return − [risk-free rate + beta × (market/benchmark return − risk-free rate)]. It compares realized portfolio return with the CAPM-implied return for the entered beta. The volatility and downside-deviation fields shown on this page do not enter the alpha equation itself.

Example

With a 12% portfolio return, 9% market return, 4% risk-free rate, and beta 1.1, CAPM-implied return is 9.5% and Jensen’s alpha is 2.5%.

How to interpret the result

Interpret the result as a modeled finance quantity, not a forecast or recommendation. Returns, rates, correlations, cash flows, fees, taxes, and market prices can change, so the most useful practice is to test a range of plausible inputs rather than treating one scenario as certain.

Limitations and notes

Jensen’s alpha inherits the limitations of CAPM and the chosen benchmark. Beta and returns are sample- and period-dependent, and alpha can change with the risk-free rate or benchmark. The volatility and downside-deviation inputs visible on this calculator are not part of the Jensen alpha equation, so they should not be interpreted as changing the alpha result.