Sortino Ratio Calculator
Calculate Sortino ratio from portfolio returns and a target return.
Penalizes only downside risk — a refinement of the Sharpe ratio for skewed return profiles.
Sortino Ratio
The Sortino ratio is a refinement of the Sharpe ratio that penalizes only downside volatility. For most investors, upside surprises are not “risk” — only losses are. Sortino addresses this by replacing standard deviation with downside deviation: the standard deviation of only the returns below a target.
Formula
Sortino = (R_p − T) / DD
Where:
- R_p = average portfolio return (annualized)
- T = target return (often the risk-free rate, but can be any minimum acceptable return)
- DD = downside deviation = √( Σ min(0, Rᵢ − T)² / N )
The downside deviation is the root-mean-square of negative excess returns only — positive returns contribute zero.
Worked Example
A portfolio with monthly returns 3%, 5%, −2%, 1%, −4%, 2%, 6%, −1%, 0%, 3%, target = 0%:
- Average R = 1.3%
- Below-target returns: −2%, −4%, −1%, treating zero/positive as zero
- DD = √((4 + 16 + 1) / 10) = √(2.1) = 1.45%
- Sortino = (1.3 − 0) / 1.45 = 0.90
For comparison, the Sharpe ratio uses all deviations (including the upside), which would understate the portfolio’s quality if returns are positively skewed.
Sortino vs Sharpe
| Metric | Risk Measure | Best For |
|---|---|---|
| Sharpe | Total volatility (σ) | Symmetric return distributions |
| Sortino | Downside-only deviation (DD) | Skewed, asymmetric returns |
| Sterling | Average drawdown | Trend-following strategies |
| Calmar | Maximum drawdown | Hedge fund, drawdown-sensitive investors |
If a strategy has positive skew (small frequent losses, occasional huge wins) — typical of trend-following or insurance writing — Sortino will rate it more favorably than Sharpe.
Interpreting the Number
| Sortino | Interpretation |
|---|---|
| < 0 | Returns below target — losing money |
| 0–1 | Sub-par |
| 1–2 | Acceptable |
| 2–3 | Good |
| > 3 | Excellent (or possible data issue) |
These thresholds are rough — context matters. A market-neutral hedge fund target of 2+ is typical; a long-only equity fund averaging 1+ is reasonable.
Choosing the Target Return
| Target choice | When to use |
|---|---|
| Risk-free rate (T-bills) | Comparing to Sharpe’s reference |
| 0% | “Did I lose money?” simple test |
| Inflation rate | Real-return preservation |
| Liability return | Pension or insurance liabilities |
| Benchmark return | Outperformance metric |
The Sortino ratio is often computed against multiple targets to show its sensitivity.
Caveats
| Pitfall | What to Watch |
|---|---|
| Few data points | Need ≥ 30 periods for stability |
| Outliers | A single huge drawdown dominates DD |
| Target choice | Subjective; affects the result |
| Time scaling | Annualize numerator and denominator together |
| Distribution assumption | Like Sharpe, assumes returns are roughly stable |
The Sortino ratio is not directly comparable across portfolios with different targets — always use the same T when ranking strategies.
History
Brian M. Rom and Frank A. Sortino introduced the ratio in 1991 to address the limitations of Sharpe for downside-averse investors. It has become the standard metric in the hedge fund and post-modern portfolio theory community.