The famous Sharpe ratio treats a big winning month as "risk." The Sortino ratio fixes that — it measures return against only the downside, the volatility that actually hurts.
Answer first: the Sortino ratio measures how much return you earned for each unit of downside risk you took. It divides your return above a target rate by the downside deviation — the volatility of only the periods that fell below that target — so good surprises don't count against you.
Sortino = (Return − Target rate) ÷ Downside deviation
Example: a 12% return against a 4% target with a 9% downside deviation gives (12 − 4) ÷ 9 ≈ 0.89. Run your own figures in the Sortino ratio calculator.
The Sharpe ratio, introduced by Nobel laureate William F. Sharpe, divides excess return by total standard deviation. That treats all volatility as bad — including the explosive up-months investors actively want. A strategy that occasionally rockets higher gets penalized by Sharpe for that very strength.
Frank A. Sortino's refinement keeps everything about the Sharpe ratio except the denominator: it swaps total volatility for downside deviation, so only returns below a "minimum acceptable return" count as risk. The result is a ratio that asks the question most investors actually care about — "how well was I compensated for the chance of losing?"
Because it strips out upside volatility, a strategy's Sortino ratio is usually higher than its Sharpe ratio. The gap between the two tells you how much of the strategy's total volatility was actually friendly upside.
Neither is "better" — they answer different questions. Use the Sharpe ratio when you want a simple, widely-quoted, like-for-like comparison and returns are roughly symmetric. Reach for the Sortino ratio when upside swings are welcome and your real worry is the downside — income portfolios, options-selling strategies and anything with a skewed return profile. Best practice is to read both. And remember: like every backward-looking ratio, the Sortino can still flatter strategies that hide rare, catastrophic tail losses, a risk the SEC repeatedly warns retail investors about (SEC: Beginners' Guide to Asset Allocation).
Educational, not advice: the Sortino ratio depends on the measurement period and the target you choose, and it cannot fully capture rare tail risk. This page is for learning only and is not financial advice. For official basics, see the U.S. SEC at investor.gov.
Measure it with the Sortino ratio calculator, compare with the Sharpe ratio calculator, gauge market risk with the beta calculator, and read risk management basics.
Last updated 25 June 2026 · Written by Mustafa Bilgic. Educational only — not financial advice.
The Sortino ratio is a measure of risk-adjusted return that divides the return earned above a target rate by the downside deviation — the volatility of only the losing periods. It rewards strategies that are steady on the way down without penalizing them for upside swings.
The Sharpe ratio divides excess return by total standard deviation, counting all volatility as risk. The Sortino ratio divides by downside deviation only. So Sharpe penalizes big up-moves while Sortino ignores them, making Sortino more relevant when returns are skewed.
Downside deviation measures how much returns vary below a chosen target. You take only the periods that fell short of the target, square those shortfalls, average them and take the square root — isolating the harmful volatility that investors actually fear.
Use the Sortino ratio when upside volatility is welcome and you mainly care about avoiding losses — common for income strategies, hedge funds and asymmetric return profiles. Read it alongside the Sharpe ratio rather than relying on either alone.