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The Sortino Ratio is a risk-adjusted return metric that measures how much return a portfolio generates per unit of downside risk. Unlike the Sharpe Ratio, which divides excess return by total standard deviation, the Sortino Ratio only penalizes the portfolio for returns that fall below a target return. Positive volatility, meaning returns above the target, does not reduce the Sortino score. This makes the Sortino Ratio more useful for evaluating investments where upside volatility is desirable.
Think of the Sortino Ratio like judging a basketball player only on their turnovers rather than all their touches: it isolates the bad outcomes from the good.
Sortino Ratio = (Portfolio Return – Target Return) / Downside Deviation
The numerator is simply the excess return above a minimum acceptable return, often called the target return or hurdle rate. Many practitioners use 0% or a risk-free rate as the target. The denominator is the downside deviation, which measures only the standard deviation of returns that fall below the target. Returns above the target are excluded from the denominator entirely.
The Sortino Ratio was developed by Frank Sortino, a finance professor at San Francisco State University, who argued that the Sharpe Ratio unfairly penalized strategies with positive volatility such as strong upside months in a trend-following strategy.
A Sortino Ratio above 1.0 generally indicates the portfolio is generating more return per unit of downside risk than the target hurdle. A ratio above 2.0 is considered strong by most practitioners. A ratio below 1.0 suggests the strategy is not adequately compensating investors for the downside risk being taken.
Like all ratios, the Sortino Ratio is most meaningful in comparison: comparing one strategy against another, or against a benchmark index. A hedge fund with a Sortino Ratio of 1.5 and a benchmark with a Sortino Ratio of 0.8 suggests the fund is generating better downside-adjusted returns.
| Sortino Ratio | Sharpe Ratio | |
|---|---|---|
| Denominator | Downside deviation only (returns below target) | Total standard deviation (all returns) |
| Penalizes upside volatility | No | Yes |
| Better for | Strategies with asymmetric upside (trend-following, options writing) | Broadly symmetric return distributions |
The Sortino Ratio is especially useful when evaluating strategies that intentionally carry upside optionality. A long-bias equity fund that occasionally has big winning months will look less favorable under the Sharpe Ratio than it deserves, because the Sharpe penalizes those winning months as volatility. The Sortino Ratio credits those wins and only penalizes the losses.
It is also valuable for comparing strategies with different skew profiles, meaning cases where the return distribution is not symmetric.
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