Ten points of excess return bought with fifteen points of volatility
A 12% return against a 2% risk-free rate is 10 points of excess — the part that was not available for free. Dividing by 15% of standard deviation gives 0.67: two-thirds of a point of excess return for each point of volatility endured.
Sharpe = (Rp − Rf) / σp
The risk-free subtraction is what makes the ratio meaningful. A fund returning 12% when Treasury bills pay 2% did something; the same 12% when bills pay 11% did almost nothing. Without that subtraction, a high-return figure in a high-rate environment would flatter a manager who added no value at all.
Under 1 is common, over 2 is rare, and the number moves with the period
Conventional reading puts anything below 1 as unremarkable, 1 to 2 as good, and above 2 as excellent — but those are rules of thumb from long-run equity data, not fixed standards. A broad equity index has historically delivered something in the region of 0.4 to 0.6 over long periods, so a fund at 0.67 is not underperforming the market on this measure.
The ratio also depends on the measurement period. Computed on monthly data and annualised, it differs from one computed on annual figures, and a short window can produce a spectacular ratio purely because the period happened to be calm. Compare Sharpe ratios only when both were computed the same way over the same span.
Standard deviation punishes a good month exactly as hard as a bad one
Standard deviation measures dispersion in both directions. A fund that occasionally returns 30% in a month is penalised for it, identically to one that occasionally loses 30%. For most investors those are not the same experience, and a strategy with large positive skew can score poorly on Sharpe while being exactly what someone wanted.
The Sortino ratio replaces the denominator with downside deviation, counting only returns below a threshold. On the same 10 points of excess, a 10% downside deviation gives a Sortino of 1.00 against this Sharpe of 0.67 — and the gap between the two is itself informative, because it says how much of the volatility was upside.
A normal distribution, which market returns are not
Standard deviation summarises a distribution in one number, and it does that well only when the distribution is roughly normal. Real return series have fat tails: extreme moves happen far more often than a normal distribution predicts, and the ratio understates the risk of exactly the events that matter most.
Strategies that sell insurance-like exposure — writing options, carry trades, credit risk — are the sharpest case. They produce small steady gains and rare large losses, which yields an excellent Sharpe ratio right up until the tail event arrives. A high ratio on a short history of such a strategy is a description of the calm period, not of the risk.
Frequently Asked Questions
What is the Sharpe ratio?
The Sharpe ratio measures how much excess return a portfolio earns for each unit of risk, where risk is the standard deviation of returns. It is the most widely used way to compare investments on a risk-adjusted basis.
What is a good Sharpe ratio?
It varies by asset class and time period, so treat thresholds loosely. Many investors regard a ratio above 1 as good and a ratio below 0 as worse than holding a safe asset, but the figure is most meaningful when compared against similar portfolios.
What is the difference between the Sharpe ratio and the Sortino ratio?
Both divide excess return by a measure of risk. The Sharpe ratio uses total standard deviation, counting upside and downside swings alike, while the Sortino ratio uses only downside deviation, so it focuses purely on harmful volatility.
Why does the Sharpe ratio use the risk-free rate?
Because you can earn the risk-free rate without taking risk. Subtracting it leaves the excess return, which is the portion you were actually compensated for by taking on volatility.
Can the Sharpe ratio be negative?
Yes. A negative Sharpe ratio means the portfolio returned less than the risk-free rate, so an investor would have done better in a safe asset over that period without taking on the volatility.
Does a higher Sharpe ratio guarantee a better investment?
No. A higher ratio indicates more efficient past returns relative to risk, but it is based only on historical inputs and offers no guarantee of future performance.
Sources & References
Figures on this page are checked against primary, authoritative sources. Links open in a new tab.
Returns are roughly normally distributed, so standard deviation captures the relevant risk.
The risk-free rate and return are measured over the same period as the standard deviation.
Figures are estimates; investment returns are not guaranteed and vary with market conditions.
Where it stops
It penalises upside volatility as much as downside, which can understate the appeal of consistently positive but variable returns.
It is unreliable when the standard deviation is very small or returns are highly skewed; the tool returns 0 if volatility is zero.
A single Sharpe ratio describes only your inputs and period and does not predict future results.
Related Calculators
Sortino RatioThe Sharpe idea with downside deviation as the denominator, so upside volatility is not treated as risk.
Standard DeviationSample and population standard deviation, plus variance, mean, median, quartiles, z-scores, outliers, and confidence intervals.
Maximum DrawdownThe largest peak-to-trough fall in a value series, and the gain required to recover from it.
Expected ReturnProbability-weighted return across scenarios, with the best and worst cases and a check that probabilities sum to 100%.
Holding Period ReturnTotal return over a holding period, split into the capital gain and the income yield that produced it.
Annualized ReturnThe compound annual rate behind a total return, with the growth multiple alongside it.
CAGRThe compound annual growth rate between two values, or the end value a rate reaches and the years it needs, with the path year by year.
Rule of 72Years to double from a rate, or the rate to double in a set time, by the rule of 72 — with the exact answer and the error beside it, plus the rules of 114 and 144.
Returns are assumptions, not guarantees. Actual results may vary because of market performance, taxes, fees, inflation, and timing. This is an educational projection, not investment advice.
Published the calculator with its formula, worked example, assumptions, limitations and a bespoke guide, and added an automated formula test suite covering it.
Verified that the risk-free rate is subtracted before dividing, since a high return in a high-rate environment is not the same achievement as the same return when cash pays nothing.
Frequently Asked Questions now show on the page: 6 answers, checked in a page-by-page audit.
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