What is Sharpe Ratio?
Article last updated: September 10, 2026
The Sharpe Ratio is a risk-adjusted return ratio that compares an investment's return to its risk. It was created in the 1960s by Nobel laureate William Sharpe as a way to judge whether an investment portfolio was rewarded fairly for the volatility it took on.
Key takeaways
- The Sharpe Ratio measures how much return an investment earned above the risk-free rate for each unit of volatility it took on.
- The Sharpe Ratio is calculated as the investment's return minus the risk-free rate, divided by the standard deviation of the investment's returns.
- A Sharpe Ratio above 1.0 is generally considered decent and above 2.0 is strong, while a negative Sharpe Ratio means the investment returned less than the risk-free rate.
- The Sharpe Ratio treats all volatility as risk, so it penalises unusually large gains as heavily as large losses and ignores liquidity and tail risk.
- The Sharpe Ratio is backward-looking, computed from historical returns rather than future projections.
What is the Sharpe Ratio?
The Sharpe Ratio is a measure of risk-adjusted return that tells you how much excess return an investment produced for each unit of volatility. Excess return here means the return above the risk-free rate, such as the yield on a short-term Treasury bond.
Two investments can post the same headline return while one of them swung violently to get there. The Sharpe Ratio separates those two cases by dividing the excess return by the standard deviation of returns, the standard statistical measure of how widely returns scatter around their average. Because it reduces to a single number, the Sharpe Ratio lets you score a concentrated tech portfolio and a bond fund on the same scale.
How is the Sharpe Ratio calculated?
The Sharpe Ratio is calculated by subtracting the risk-free rate from the investment's return and dividing the result by the standard deviation of the investment's returns. You need those three inputs and nothing else.
Sharpe Ratio = (Investment Return - Risk-Free Rate) / Investment Return Standard Deviation
The three inputs are:
- Investment return. The return the investment or portfolio actually delivered over the measurement period.
- Risk-free rate. The return available with essentially no risk over the same period, usually proxied by a short-term government bond yield such as the 3-month Treasury bill.
- Standard deviation of returns. How much the investment's periodic returns varied around their average, expressed in the same units as the return.
All three inputs must cover the same period at the same frequency. Mixing a monthly return with an annual risk-free rate produces a Sharpe Ratio that means nothing.
Getting the return input right is the tedious part, because a real portfolio has deposits, withdrawals, dividends and holdings at several brokers. Portseido calculates time-weighted and money-weighted returns for every portfolio automatically from your transaction history, so you have a defensible return figure to feed into the Sharpe Ratio without rebuilding a spreadsheet each time.
Sharpe Ratio calculation example
A stock that returned 10% over the past year, against a 3% risk-free rate, with a 5% standard deviation of returns, has a Sharpe Ratio of 1.4.
Working through the Sharpe Ratio formula, which is the investment's return minus the risk-free rate divided by the standard deviation of its returns:
Sharpe Ratio = (10% - 3%) / 5% = 1.4
With a Sharpe Ratio of 1.4, the stock produced 1.4 percentage points of return above the risk-free rate for every 1 percentage point of volatility. Put differently, the investor was paid 1.4 units of excess return for each unit of risk carried.
Now compare it to a second stock that returned 14% over the same year with a standard deviation of 12%. Its Sharpe Ratio is (14% - 3%) / 12% = 0.92. The second stock earned more in absolute terms, but the first stock was the better risk-adjusted investment.
What is a good Sharpe Ratio?
A Sharpe Ratio above 1.0 is generally considered good, and a ratio above 2.0 is considered strong. The thresholds are conventions rather than rules, and they shift with the asset class and the measurement period.
| Sharpe Ratio | Common interpretation |
|---|---|
| Below 0 | The investment returned less than the risk-free rate |
| 0 to 1.0 | Sub-optimal: the return did not compensate well for the volatility |
| 1.0 to 2.0 | Decent risk-adjusted return |
| 2.0 to 3.0 | Strong risk-adjusted return |
| Above 3.0 | Excellent, but worth checking for a short measurement window or leverage |
Judge a Sharpe Ratio in context: compare it with peers in the same asset class over the same window, not with a number from a different market or a different decade.
What are the limitations of the Sharpe Ratio?
The main limitation of the Sharpe Ratio is that it uses standard deviation as its definition of risk, which means it treats every deviation from average as bad, including large gains.
- Upside is penalised. A strategy that occasionally posts a huge positive month is marked down as heavily as one that posts a huge loss.
- Tail and liquidity risk are invisible. The Sharpe Ratio does not capture the risk that an asset cannot be sold at a fair price, nor the risk of rare, severe losses.
- It is historical. The Sharpe Ratio is computed from past returns, so a high ratio describes what happened, not what will happen.
- It is easy to distort. Measuring over a short, calm window inflates the Sharpe Ratio, because the standard deviation in the denominator is temporarily small.
For that reason the Sharpe Ratio is best read alongside other measures, such as maximum drawdown, which shows the worst peak-to-trough loss a portfolio actually suffered.
How does the Sharpe Ratio compare with alpha and the Treynor Ratio?
The Sharpe Ratio, alpha and the Treynor Ratio all adjust return for risk, but each defines risk differently, so they answer different questions.
| Measure | Risk it divides by | Question it answers |
|---|---|---|
| Sharpe Ratio | Total volatility (standard deviation) | How much excess return per unit of overall volatility? |
| Treynor Ratio | Beta (market sensitivity) | How much excess return per unit of market risk? |
| Alpha | Not a ratio; a residual | How much return beat what the risk taken predicted? |
Use the Sharpe Ratio to judge a standalone portfolio, because total volatility is what its owner actually experiences. Use the Treynor Ratio when the holding sits inside an already diversified portfolio, since only its market risk survives diversification.
Frequently asked questions
Can the Sharpe Ratio be negative?
Yes. The Sharpe Ratio is negative whenever an investment's return is lower than the risk-free rate over the measurement period, because the numerator of the formula becomes negative. A negative Sharpe Ratio means the investor took on volatility and was worse off than holding a Treasury bill. Negative Sharpe Ratios cannot be meaningfully ranked against each other.
Which risk-free rate should I use in the Sharpe Ratio?
Use a government security whose maturity matches your measurement period and currency, most commonly the 3-month Treasury bill yield for a portfolio measured in US dollars. The point is consistency: whichever rate you choose, use the same one across every investment you compare, or differences in the risk-free rate will distort the ranking.
Does the Sharpe Ratio need to be annualised?
Yes, if you want to compare it with published figures, because Sharpe Ratios are conventionally quoted on an annual basis. To annualise a Sharpe Ratio built from monthly data, multiply it by the square root of 12; for daily data, multiply by the square root of 252, the approximate number of trading days in a year.
What is the difference between the Sharpe Ratio and the Sortino Ratio?
The Sharpe Ratio divides excess return by the standard deviation of all returns, while the Sortino Ratio divides excess return only by the standard deviation of negative returns. The Sortino Ratio therefore does not penalise upside volatility. It suits strategies with deliberately lopsided return profiles, where the Sharpe Ratio would understate performance.
Can I compare the Sharpe Ratios of two different funds?
Only if both Sharpe Ratios were calculated over the same period, at the same return frequency, and with the same risk-free rate. A fund measured over a calm two-year window will show a higher Sharpe Ratio than an identical fund measured through a crash.
How to track portfolio risk and return in Portseido
Portseido is a portfolio tracker that computes the return side of the risk-adjusted picture for you. It consolidates holdings across brokers and currencies, calculates time-weighted and money-weighted returns, tracks cost basis, dividends and yield on cost, and reports drawdown and allocation so you can see how much volatility your portfolio actually put you through. You can also benchmark a portfolio against indices and ETFs, the comparison that makes any risk-adjusted number meaningful.
It suits self-directed investors who hold assets at more than one broker and want one consistent set of performance figures. Portseido tracks and reports on your portfolio; it does not give buy or sell recommendations. There is a free plan, and paid features come with a 14-day trial that does not need a credit card. Try Portseido free