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Start Learning → Browse All Articles →A high return means little on its own — the Sharpe ratio asks how much risk you took to get there.
Two traders can post the same annual return and have taken wildly different amounts of risk to get there. The Sharpe ratio, developed by economist William Sharpe, is one of the most widely used tools for making that comparison fair.
The Sharpe ratio measures return earned per unit of total risk taken, where risk is represented by the standard deviation, or volatility, of returns. It is calculated by subtracting a risk-free rate (such as the return on a short-term government security) from the portfolio or strategy’s return, then dividing that excess return by the standard deviation of returns over the same period. A higher Sharpe ratio means more return was generated for each unit of volatility endured.
The subtraction matters because simply holding a risk-free instrument already earns a return without taking on market risk. The Sharpe ratio is really asking how much extra return you earned specifically for choosing to take on risk, rather than just parking money in a safe asset — a strategy only starts to look genuinely attractive once its return clears this baseline by a meaningful margin relative to its volatility.
As a general rule of thumb used across the investing world, a Sharpe ratio below 1 is often considered subpar, a ratio between 1 and 2 reasonable, and a ratio above 2 quite strong, though these thresholds vary somewhat by asset class and time period. What matters more than any single fixed threshold is comparing Sharpe ratios across strategies or portfolios evaluated over the same period, since it is fundamentally a comparative, not an absolute, measure.
Because it treats all volatility — both upside and downside swings — as equally undesirable, the Sharpe ratio can penalise a strategy that has occasional large upside moves just as much as one with equally large downside moves, even though most traders would only consider the downside swings to be genuinely “risky.” This is one reason the Sortino ratio, which focuses specifically on downside volatility, was developed as a complementary measure.
For a retail F&O trader, the Sharpe ratio is most useful not as a single magic number but as a consistent yardstick for comparing your own strategy’s performance across different periods, or for comparing two candidate strategies against each other on a like-for-like basis, rather than judging any single strategy in isolation.