Sharpe Ratio vs Sortino Ratio: Which Risk Measure Should You Use?
What Is the Sharpe Ratio?
The Sharpe ratio, developed by Nobel laureate William Sharpe, calculates excess return per unit of total risk. It divides the portfolio’s return above the risk-free rate by its standard deviation. Higher is better — it means more return for each unit of risk taken.
What Is the Sortino Ratio?
The Sortino ratio modifies the Sharpe ratio by replacing total standard deviation with downside deviation — only the volatility from returns below a target (usually zero or the risk-free rate). This makes the Sortino ratio more relevant for investors who care about losing money, not about upside surprises.
Sharpe vs Sortino: Side-by-Side Comparison
| Dimension | Sharpe Ratio | Sortino Ratio |
|---|---|---|
| Risk measure | Total standard deviation | Downside deviation only |
| Treats upside volatility as risk | Yes — penalizes big gains too | No — ignores upside volatility |
| Assumes normal distribution | Works best with symmetric returns | Better for skewed returns |
| Industry adoption | Universal standard | Growing — preferred by sophisticated investors |
| Typical “good” value | > 1.0 (excellent > 2.0) | > 1.5 (typically higher than Sharpe) |
| Best for | General portfolio comparison | Strategies with asymmetric returns |
| Hedge fund reporting | Standard metric | Increasingly reported alongside Sharpe |
| CFA curriculum | Core topic | Supplementary metric |
| Penalizes options strategies | Yes — high total vol from big up-moves | No — only counts downside |
| Ease of calculation | Simpler | Slightly more complex (downside deviation) |
Why the Distinction Matters
Consider two portfolios. Portfolio A returns 15% with equal upside and downside swings. Portfolio B returns 15% with the same downside but larger upside swings (more positive skew). The Sharpe ratio penalizes Portfolio B for its higher total volatility, even though the extra volatility comes entirely from outsized gains. The Sortino ratio correctly identifies that both portfolios have the same downside risk — and would rate them more similarly.
This matters a lot for strategies that generate asymmetric returns — long options positions, venture-style portfolios, momentum strategies, or any approach that aims for large occasional winners.
When to Use Each
Use the Sharpe ratio for general portfolio comparison, asset allocation decisions, and when returns are roughly normally distributed. It’s the standard benchmark and everyone understands it. Use the Sortino ratio when evaluating strategies with skewed return profiles, when downside protection is the primary concern (retirees, endowments), or when comparing strategies that explicitly aim for positive skew.
Key Takeaways
- Sharpe uses total volatility; Sortino uses only downside volatility — a more investor-relevant risk measure
- Sharpe penalizes upside surprises; Sortino doesn’t — making it better for asymmetric strategies
- Sharpe is the industry standard for general comparison; Sortino is gaining traction for nuanced analysis
- When Sortino >> Sharpe, the portfolio has favorable positive skew (upside-driven volatility)
- Use both ratios together alongside max drawdown for a complete risk picture
Frequently Asked Questions
Is a higher Sharpe or Sortino ratio always better?
Yes, higher is always better for both — it means more return per unit of risk. But context matters: a Sharpe of 2.0 is exceptional for a long-only equity fund but merely decent for a market-neutral hedge fund. Compare ratios within the same strategy type and time period.
What is a good Sharpe ratio?
For public equity portfolios, a Sharpe ratio above 0.5 is decent, above 1.0 is good, and above 2.0 is excellent. The S&P 500’s long-term Sharpe ratio is roughly 0.4–0.5. Consistent Sharpe ratios above 1.0 over long periods are rare and valuable.
Why is the Sortino ratio typically higher than the Sharpe ratio?
Because downside deviation is usually smaller than total standard deviation (since it only counts negative returns). With a smaller denominator and the same numerator, the Sortino ratio will typically be higher than the Sharpe ratio for the same portfolio — especially if returns have positive skew.
Do both ratios work for individual stocks?
Technically yes, but they’re designed for portfolio-level analysis. Individual stocks have idiosyncratic risk that can be diversified away, so risk-adjusted metrics are more meaningful at the portfolio level. For single stocks, consider alpha or the Treynor ratio instead.
Can the Sharpe ratio be negative?
Yes. A negative Sharpe ratio means the portfolio returned less than the risk-free rate — you would have been better off in Treasury bills. A negative Sortino ratio carries the same interpretation. Negative risk-adjusted ratios indicate the strategy destroyed value relative to a riskless alternative.