Jensen's Alpha Calculator

Jensen's alpha measures the abnormal return of a portfolio over and above the expected return predicted by the Capital Asset Pricing Model (CAPM). The calculation is a two-step process. First, the actual portfolio return is derived from the starting and ending portfolio values: Port Return = (Ending Port - Beginn Port) / Beginn Port. Second, Jensen's alpha is computed using the formula: Jensen Alpha = Port Return - (Free + Port Beta * (Market Rate Return - Free)), where 'Free' represents the risk-free rate of return and 'Port Beta' measures the portfolio's volatility relative to the broader market.

Imagine you manage a stock portfolio that began the year valued at $100,000 and grew to $115,000 by year-end. First, we calculate the portfolio return: ($115,000 - $100,000) / $100,000 = 0.15 or 15%. Next, suppose the risk-free rate (Free) is 3% (0.03), the market rate return is 10% (0.10), and your portfolio beta is 1.2, indicating higher volatility than the benchmark. According to CAPM, your expected return is 3% + 1.2 * (10% - 3%) = 11.4%. Finally, subtracting this expected return from your actual return yields: 15% - 11.4% = +3.6%. Your Jensen's alpha is +3.6%, demonstrating genuine outperformance given the risk assumed.

When analyzing your calculated alpha, always compare portfolios against a relevant benchmark index rather than a generic market proxy. Keep in mind that a single year of positive alpha may be the result of luck rather than skill; evaluating multi-year rolling windows provides a more reliable metric. Additionally, remember that high alpha often comes paired with higher portfolio volatility or leverage.