Jensen's Alpha — What Is Alpha in Investing?

Quick Answer

Alpha (α), also called Jensen's alpha, is a measure of excess investment return beyond what the CAPM predicts for a given risk level (beta) — in short, how much more or less you earned than you should have for the risk taken. It is calculated as α = Rp − [Rf + β × (Rm − Rf)], so a portfolio returning 15% against a model expectation of 13.8% has +1.2% alpha. A positive alpha means a manager added value; a negative one means they subtracted it. It matters because 80–90% of active funds generate negative alpha after fees, the core case for passive ETF investing.

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Definition

Alpha (α), also known as Jensen's alpha, is a measure of excess investment return beyond what the CAPM (Capital Asset Pricing Model) predicts for a given risk level (beta).

Simply put: alpha tells you how much more (or less) you earned than you should have, considering the risk you took.

Interpretation

• α > 0 — portfolio beat the benchmark after adjusting for risk (manager added value)
• α = 0 — portfolio performed exactly as the model predicted
• α < 0 — portfolio lost to the benchmark (manager subtracted value)

Formula

α = Rp - [Rf + β × (Rm - Rf)]

Where:

• Rp = actual portfolio return
• Rf = risk-free rate
• β = portfolio beta
• Rm = market return (benchmark)

Example

Your portfolio earned 15%, the market (S&P 500) 12%, risk-free rate 3%, portfolio beta 1.2.

α = 15% - [3% + 1.2 × (12% - 3%)]
α = 15% - [3% + 10.8%]
α = 15% - 13.8% = +1.2%

Your alpha is +1.2% — you earned 1.2% more than the model predicted for your risk level.

Why is alpha important?

Alpha is a key metric for evaluating:

• Fund managers — is the active fund worth higher fees?
• Your portfolio — do your decisions add value vs simple index ETF?

Studies show that 80–90% of active funds generate negative alpha after fees. That's why many experts recommend passive investing (ETFs).

Alpha vs beta

• Beta = how much market risk you're taking
• Alpha = how much additional return you're generating beyond that risk

Passive investors aim for beta = 1 and alpha = 0 (same results as the market). Active investors seek positive alpha.

How Freenance can help?

Freenance can calculate your portfolio's alpha by comparing results to a selected benchmark. Check if your investment decisions truly add value — or whether it's better to switch to a simpler ETF portfolio.

👉 Measure your portfolio's alpha with Freenance — freenance.io

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FAQ

What does positive alpha mean?

Positive alpha means a portfolio earned more than the CAPM model predicted for its risk level (beta). In practice, it suggests the manager or strategy added value above what a passive benchmark exposure would have delivered. Past alpha does not guarantee future alpha — this is not investment advice.

Is alpha the same as total return?

No. Total return is the raw gain or loss on a portfolio, while alpha is the portion of that return left after subtracting the return explained by market exposure (beta times benchmark return) and the risk-free rate. Two portfolios with the same total return can have very different alphas.

Why do most active funds show negative alpha?

Active funds charge management and performance fees that drag down net returns, and consistently beating a broad benchmark is statistically difficult. Multiple long-term studies show 80–90% of active funds underperform their benchmark net of fees over 10–15 year horizons.

Can a passive ETF have alpha?

A passive ETF tracking a broad index targets beta close to 1 and alpha close to 0 by design, minus tracking error and fees. Small positive or negative alpha can appear from securities lending revenue, optimisation, or expense ratios, but it is not the goal of passive investing.

How can I estimate alpha for my own portfolio?

You need your portfolio return, a relevant benchmark return, the risk-free rate, and an estimate of your portfolio beta over the same period. Plug them into the formula α = Rp − [Rf + β × (Rm − Rf)] — Freenance can help compare your portfolio return against a chosen benchmark to inform that calculation.