What Alpha Means
Alpha is the return you earn beyond what your risk level would have delivered anyway. Here is how to calculate it, why raw returns can mislead and what a real alpha estimate looks like.
Beating the market fairly
If your portfolio rose 20% while the market rose 15%, did you add value? Not necessarily. If you took far more risk than the market, you might have been expected to earn more. Alpha measures the return left over after accounting for risk. Positive alpha means you did better than your risk level predicts; negative alpha means you did worse.
A simple formula
A common version compares your return with what the market would have given at your level of market risk, called beta. Expected return equals the risk-free rate plus beta times the market’s return above the risk-free rate. Alpha is your actual return minus that expected return.
| Step | Example |
|---|---|
| Risk-free rate | 4% |
| Market return | 10% |
| Portfolio beta | 1.2 |
| Expected return | 4% + 1.2 × (10% − 4%) = 11.2% |
| Actual return | 12% |
| Alpha | 12% − 11.2% = 0.8% |
Hypothetical example.
Why raw returns mislead
In our price data, over the year to Sept. 17, 2026, AMD rose about 245% while SPY rose about 15%. AMD also moved about three times as much as the market day to day. Some of that gain was a reward for risk; some was genuine outperformance. Alpha separates the two, though estimates from one year are very noisy.
Returns look different once you account for risk.
Alpha in practice
- Alpha is always measured against a benchmark; the wrong benchmark gives the wrong answer.
- Short periods produce unreliable alpha estimates.
- Fees reduce alpha directly: a fund with 1% of alpha before fees and 1% in fees has none.
Key takeaways
- Alpha is return beyond what your risk level predicts.
- Expected return = risk-free rate + beta × market excess return.
- Raw returns can mislead without accounting for risk.
- Fees reduce alpha directly.