Sortino Ratio
A risk-adjusted return measure like the Sharpe ratio, but it penalizes only downside volatility instead of total volatility.
What it is
The Sortino Ratio, developed by Frank Sortino, measures how much return an investment earns above a target for each unit of harmful (downside) risk it takes. It takes the return above a minimum acceptable return (MAR), often the risk-free rate or simply zero, and divides it by downside deviation, which counts only the volatility of returns that fell below that target. Returns above the target are treated as good and contribute nothing to the denominator. It is a refinement of the Sharpe ratio for investors who do not view upside swings as risk.
Why it matters
Because it ignores upside swings, the Sortino ratio gives a fairer read on strategies with lumpy or skewed returns, where big up moves would unfairly inflate the Sharpe ratio's denominator. The main pitfall is a noisy denominator: if an investment had few periods below the target, downside deviation is estimated from a handful of observations and a single outlier can swing the ratio wildly, so a sky-high Sortino on a short, calm track record can be a mirage rather than skill.
How it's calculated
Subtract the minimum acceptable return (commonly the risk-free rate or zero) from the investment's return to get excess return, then divide by downside deviation. Downside deviation is found by taking each period's shortfall below the target, squaring it (counting above-target periods as zero), averaging those squared shortfalls over all periods, and taking the square root. Both numerator and denominator should cover the same period and frequency before comparing names.
How Quintarthai uses it
Risk-adjusted and volatility metrics surface on a company's deep-analysis page at /app/, where you can study a name's downside-risk profile alongside click-to-source receipts. Learn the related building blocks in the Knowledge Base.