Sortino Ratio
A risk-adjusted performance metric similar to the Sharpe ratio, but only penalizes downside volatility — upside volatility is considered beneficial, not risky.
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Explained Simply
The Sortino ratio improves on the Sharpe ratio by distinguishing between harmful downside volatility and harmless upside volatility. Formula: (Portfolio Return - Risk-Free Rate) / Downside Deviation. A strategy that has big winning days and small losing days will have a higher Sortino than Sharpe, reflecting the asymmetric return profile. Above 2.0 is considered excellent, 1.0-2.0 is good, and below 1.0 suggests inadequate risk-adjusted returns. For day traders, the Sortino ratio is often more useful than the Sharpe ratio because day trading returns tend to be positively skewed — occasional big wins with controlled small losses.
How to Calculate the Sortino Ratio
The Sortino ratio formula is: (Portfolio Return - Target Return) / Downside Deviation.
Target return: Often the risk-free rate (same as Sharpe), but some traders use 0% or a minimum acceptable return (MAR) as the target. Using 0% means any negative return counts as "downside."
Downside deviation: Only considers returns below the target. Step 1: Filter returns to keep only those below your target. Step 2: Square each negative excess return. Step 3: Average the squared values. Step 4: Take the square root. This is conceptually similar to standard deviation but ignores positive returns entirely.
Example: A strategy has monthly returns of +5%, -2%, +8%, -1%, +3%, +6%. Using a 0% target, only -2% and -1% count as downside. Downside deviation = sqrt(mean(0.02² + 0.01²)) = sqrt(0.00025) = 1.58%. Average return = 3.17%. Sortino = 3.17% / 1.58% = 2.0.
Annualizing: Multiply the monthly Sortino by sqrt(12) to annualize, or multiply the daily Sortino by sqrt(252). The same Sortino of 2.0 monthly becomes ~6.9 annualized.
Benchmarks: Annual Sortino above 1.0 = acceptable. 2.0-3.0 = good. Above 3.0 = excellent. Most well-managed day trading strategies should target Sortino ratios of 2.0 or higher because the tight stop-loss discipline should produce positively skewed returns.
Sortino vs Sharpe: When Each Metric Matters
The Sortino and Sharpe ratios answer slightly different questions about strategy quality.
When Sharpe is better: For strategies with roughly symmetric returns (equal upside and downside volatility), Sharpe and Sortino produce similar results. Mean-reversion strategies, market-neutral strategies, and index fund analysis work fine with Sharpe.
When Sortino is better: For strategies with asymmetric returns — occasional large winners with controlled small losers — the Sortino ratio is more appropriate. Trend-following strategies, breakout strategies, and day trading with strict stop-losses all produce positively skewed returns where the Sharpe ratio unfairly penalizes upside volatility. A strategy that occasionally has a +10% day (increasing total volatility) should not be penalized for that — the Sortino ratio correctly ignores those positive outliers.
Practical example: Strategy A returns 2% monthly with 3% standard deviation and 1.5% downside deviation. Sharpe = 2/3 = 0.67. Sortino = 2/1.5 = 1.33. Strategy B returns 2% monthly with 4% standard deviation and 1.5% downside deviation. Sharpe = 2/4 = 0.50. Sortino = 2/1.5 = 1.33. Both strategies have identical downside risk, but Strategy B has larger upside swings. Sharpe penalizes B; Sortino correctly treats them as equally good from a risk perspective.
Rule of thumb: Report both metrics. If your Sortino is significantly higher than your Sharpe (e.g., 2x or more), your strategy has desirable positive skew. If they are similar, returns are roughly symmetric.
How to Use Sortino Ratio
- 1
Gather Downside Return Data
Collect daily or monthly returns and identify only the returns below your minimum acceptable return (MAR, often 0% or the risk-free rate). These negative returns represent the downside deviation — the risk you actually care about.
- 2
Calculate Downside Deviation
Square each return below the MAR, average those squared values, and take the square root. This is similar to standard deviation but only measures the 'bad' volatility — upside volatility (big gains) is ignored because gains aren't risk.
- 3
Compute the Sortino Ratio
Sortino = (Portfolio Return - MAR) ÷ Downside Deviation. If your annualized return is 18%, MAR is 4%, and downside deviation is 10%: Sortino = (18% - 4%) ÷ 10% = 1.40. A higher Sortino is better — it means more return per unit of downside risk.
- 4
Compare to Sharpe Ratio
The Sortino ratio is always ≥ the Sharpe ratio for the same strategy. If your Sortino is much higher than your Sharpe, your upside volatility is high (you have large positive outlier returns) — this is a good sign. If they're similar, your volatility is symmetric.
- 5
Use Sortino for Strategy Comparison
When choosing between strategies, the Sortino ratio may be more informative than Sharpe. A strategy with volatile upside (big winners) but controlled downside (small losers) will have a high Sortino and may be preferable to a strategy with similar Sharpe but symmetric volatility.
Frequently Asked Questions
What is the Sortino ratio?
The Sortino ratio is a risk-adjusted performance metric that measures how much return a strategy generates per unit of downside risk. Unlike the Sharpe ratio, which penalizes all volatility equally, the Sortino ratio only counts negative returns as risk. This makes it a better measure for strategies with asymmetric returns — where big upside days should be rewarded, not penalized.
What is a good Sortino ratio?
An annualized Sortino ratio above 1.0 is acceptable, 2.0-3.0 is good, and above 3.0 is excellent. Day trading strategies with disciplined stop-losses typically achieve Sortino ratios of 2.0-4.0 because they produce positively skewed returns. A Sortino ratio significantly higher than the Sharpe ratio for the same strategy indicates desirable positive skew — the strategy has larger winners than losers.
How Tradewink Uses Sortino Ratio
Tradewink's trade analytics calculate both Sharpe and Sortino ratios for each strategy and the overall portfolio. The RL Strategy Selector incorporates downside-adjusted returns when evaluating strategy performance, effectively using a Sortino-like metric to allocate capital toward strategies that limit downside risk while capturing upside.
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See Sortino Ratio in real trade signals
Tradewink uses sortino ratio as part of its AI signal pipeline. Get daily trade ideas with full analysis — free to start.