Jensen's Alpha Calculator

How to use this calculator

Enter four values: your Portfolio Return (annual return in %), the Market Return (S&P 500 or your relevant benchmark for the same period), the Risk-Free Rate (current 3-month T-bill yield), and your Portfolio Beta (sensitivity to benchmark moves).

The calculator computes the CAPM expected return, then measures how far your actual return is above or below it. That gap is Jensen’s alpha.

The CAPM formula

Where:

• α = Jensen’s alpha
• Rp = Portfolio return (actual, annualized)
• Rf = Risk-free rate
• β = Portfolio beta
• Rm = Market return (benchmark)

The term in brackets is the CAPM expected return — what the portfolio should have earned given its beta. CAPM says: if you take on more market risk (higher beta), you should earn a proportionally higher return. Jensen’s alpha is the excess above that prediction.

Positive alpha: the manager delivered above the CAPM prediction. Negative alpha: the manager fell short of what beta exposure alone should have produced.

Alpha interpretation table

Jensen’s Alpha	Interpretation
Below −3%	Significant underperformance; active management destroyed value
−3% to −1%	Below average; likely worse than a passive equivalent after fees
−1% to 0%	Slight underperformance; common after fees for most active funds
~0%	In line with CAPM prediction; neutral performance
0% to +2%	Above average; modest outperformance
+2% to +5%	Strong; warrants checking persistence and statistical significance
Above +5%	Exceptional; very likely not sustained; scrutinize methodology

Most active equity funds in the U.S. produce alpha between −2% and +1% gross of fees. After a 1–1.5% expense ratio, the median net alpha is negative. This is not a controversial claim — it’s the consistent finding from four decades of academic research on mutual fund returns.

If a fund advertises alpha of +6% or more, the first question to ask is: over what period, and does it survive replication with longer data? Short-period alpha is the easiest thing to manufacture with hindsight selection.

What the Security Market Line means

CAPM places every portfolio on a theoretical line called the Security Market Line (SML). The SML maps beta to expected return: zero beta earns the risk-free rate, beta 1.0 earns the market return, beta 1.5 earns 1.5 times the market risk premium plus the risk-free rate.

Jensen’s alpha is the vertical distance between a portfolio’s actual return and the SML. Portfolios above the line have positive alpha. Portfolios below have negative alpha. Portfolios on the line have alpha = 0 and are priced exactly as CAPM predicts.

In a perfectly efficient market, all portfolios would sit on the SML and alpha would be zero everywhere. The fact that some funds produce persistent positive alpha is either evidence of genuine skill or evidence that CAPM is missing a risk factor the fund is actually bearing. Both interpretations are debated.

For practical purposes, if a fund sits consistently above the SML for 10+ years across multiple market environments, that’s meaningful evidence of skill — or at minimum, an uncaptured edge worth studying.

Why most active funds have negative alpha after fees

The data on this is stark. S&P’s SPIVA reports show that over 15-year periods, roughly 85–90% of actively managed large-cap U.S. equity funds underperform their benchmark index after fees.

The mechanics are simple. Active management is a zero-sum game at the gross level: for every fund that beats the index, another must underperform by the same amount. After fees, the average active fund must underperform by the amount of its expense ratio. With typical expense ratios of 0.7–1.5% for actively managed funds versus 0.03–0.10% for index funds, the cost differential alone accounts for most of the underperformance.

Jensen’s alpha captures this precisely. A fund with +0.8% gross alpha but a 1.2% expense ratio has a net alpha of approximately −0.4%. The manager added value before fees; the fund did not after fees.

This doesn’t mean active management is never worthwhile. In specific areas — small-cap emerging markets, high-yield credit, certain alternatives — skilled managers can potentially find persistent edges where markets are less efficient. The evidence for alpha in large-cap U.S. equities is much weaker.

When alpha is real vs luck

A one-year alpha of +5% tells you almost nothing about skill. Return series are noisy. Any fund can outperform in a single year through luck.

To distinguish skill from luck, you need statistical significance. The t-statistic for alpha needs to exceed about 2.0 for 95% confidence. Given typical return volatility, this requires approximately 30–60 monthly observations (3–5 years) at a minimum. For smaller alphas, you need closer to 10 years.

Practical rules:

• 3-year alpha: preliminary signal only. Don’t act on it without more.
• 5-year alpha: worth paying attention to, especially if it persists across a drawdown.
• 10-year alpha, across at least one bear market: this is the evidence tier that matters.

Also check that the alpha is consistent. A fund that earned +15% alpha in year one and then lost −12% alpha in years two and three has a positive 3-year average but erratic actual outperformance. What you want is steady, consistent positive alpha each year — that pattern is the fingerprint of genuine skill rather than a single good year pulling up the average.

Comparing alpha across time periods

Jensen’s alpha is not stationary. A manager’s alpha in one market regime can look completely different in another.

Consider a manager with a value-oriented strategy. Value stocks massively outperformed growth from 2000–2007, generating strong alpha during that period. They underperformed dramatically from 2010–2020, generating negative alpha. A manager measured only over 2000–2007 looks like a genius. Measured over 2010–2020, the same manager looks like a bad bet.

This is why comparing alpha across different time periods is essential. If you see strong alpha claims from a fund, ask specifically:

• What were the market conditions during that period?
• Did the alpha persist through 2008–2009 (the financial crisis)?
• Did it persist through 2020 (the COVID crash)?
• Is the alpha present in both bull and bear years, or only one?

A manager who outperformed in 2019 (a strong bull year for growth stocks) but posted −3% alpha in 2022 (a down year) may simply have had high beta to the growth factor — not actual skill. Jensen’s alpha measures outperformance above beta, but multi-factor models have shown that many reported alphas can be explained by exposure to known risk factors like value, momentum, and quality.

Alpha vs information ratio

Jensen’s alpha tells you the size of outperformance. The information ratio tells you its consistency.

Information Ratio = Alpha / Tracking Error

Where tracking error is the standard deviation of the difference between the fund’s return and the benchmark return each period.

A fund with Jensen’s alpha of +4% but tracking error of 10% has an information ratio of 0.40. A fund with alpha of +2% and tracking error of 2.5% has an information ratio of 0.80. The second fund is more valuable to own because it delivers consistent outperformance without large swings.

Good information ratios:

• 0.5 = acceptable
• 0.75 = good
• 1.0+ = excellent, rare at scale

For evaluating active managers, I’d argue the information ratio is more useful than Jensen’s alpha alone. It normalizes by consistency, which matters more than peak outperformance in any single year.

Practical use: manager selection and performance attribution

When evaluating an active manager, alpha is one piece of the puzzle.

Step 1: Calculate gross alpha. Use this calculator with the fund’s gross-of-fees return, the benchmark return, the T-bill rate, and the fund’s beta. This tells you whether the manager added value before costs.

Step 2: Calculate net alpha. Subtract the expense ratio. If gross alpha is +1.5% and the expense ratio is 1.8%, net alpha is −0.3%. The manager outperformed gross but the fund underperformed net.

Step 3: Check persistence. Run the same calculation for each of the last 5 years separately. If alpha is positive in 3 out of 5 years including at least one down year, that’s a meaningful signal. Positive alpha only during bull years is a red flag.

Step 4: Check factor exposures. A fund claiming +3% alpha might simply have had high exposure to momentum stocks. Run the return through a 3-factor or 5-factor Fama-French model to see how much “alpha” survives after controlling for known factors. Most doesn’t.

Step 5: Look at the information ratio. Consistent small alpha beats inconsistent large alpha for long-term compounding. A fund with an information ratio above 0.5 is doing something repeatable.

The fee trap: gross alpha vs net alpha

This is the most important practical insight in manager evaluation, and it’s where most retail investors go wrong.

Active managers are compensated on gross performance. They earn their fee regardless of whether you do well net of that fee. A manager generating +1.2% gross alpha is genuinely skilled. But if their fund charges 1.5%, you’re paying 1.5% for 1.2% of value. You’re better off in a 0.05% index fund.

The calculation is straightforward:

Net alpha = Gross alpha − Expense ratio − Transaction costs

For most actively managed mutual funds, the total cost of ownership — expense ratio plus transaction costs from portfolio turnover — runs 1.5–2.5% per year. The median gross alpha across all active funds is close to zero. The median net alpha is therefore −1.5% to −2.5%.

There are exceptions. Some active funds in genuinely less-efficient markets (small international stocks, high-yield bonds, private credit) earn gross alpha consistently above 2–3% and charge reasonable fees. In those cases, the net alpha is positive and active management is worth paying for.

For U.S. large-cap equity, where information is instantly priced by thousands of sophisticated participants, the bar for net positive alpha is very high. The data says most active managers don’t clear it. Jensen’s alpha, measured properly over a full market cycle and net of fees, is the most honest way to check whether any individual fund does.