The Sharpe ratio: what it is and how to use it
The most widely used measure for comparing investments by their risk, explained step by step, with its strengths and its pitfalls.
Oct 22, 2026 · 4 min read
Two investments returned 12% last year. Are they equally good? Not necessarily. If one got to that 12% with gentle ups and downs and the other with 30% drops along the way, the first was far more efficient. The Sharpe ratio exists precisely to compare investments while taking into account the risk it took to earn their return.
The idea in one sentence
The Sharpe ratio measures how much extra return you get for each unit of risk you take.
In words, it's calculated like this:
(Investment return − risk-free return) ÷ volatility
- Risk-free return: what you'd earn without taking risk, for example in a savings deposit or short-term government bills.
- Extra return: what you earn above that, which is your reward for taking risk.
- Volatility: how much the investment goes up and down. It's the measure of risk.
A simple example
Illustrative numbers. Suppose the risk-free rate is 4% a year and you compare two funds:
| Fund A | Fund B | |
|---|---|---|
| Annual return | 12% | 12% |
| Volatility | 10% | 25% |
| Extra return | 8% | 8% |
| Sharpe | 0.8 | 0.32 |
Both earned the same, but fund A did it with far fewer jolts. For each unit of risk, A delivered more than twice the reward.
How to interpret the number
There's no universal rule, but as a general guide:
- Below 0: the investment returned less than the risk-free alternative. You took risk for nothing.
- Between 0 and 0.5: a low reward for the risk taken.
- Between 0.5 and 1: reasonable.
- Above 1: a very good risk-return trade-off, at least over the period measured.
Careful: these ranges depend on the period and the type of asset. A high Sharpe during an exceptional year may never be repeated.
Why your country's risk-free rate matters
The risk-free rate isn't the same everywhere. In Brazil or Colombia, interest rates tend to be much higher than in the United States, the euro area or Switzerland. That changes the Sharpe: an investment returning 10% a year looks attractive if the safe alternative pays 4%, but much less so if it pays 12%.
That's why, in the optimizer, the risk-free rate changes with your base currency, and you can edit it. We use approximate default values by currency; if you know your country's current rate, adjust it.
The maximum-Sharpe portfolio
One of the optimizer's methods is Maximum Sharpe: among all possible combinations of your assets, it looks for the one with the highest Sharpe ratio. On the efficient frontier it's the point where a line drawn from the risk-free rate touches the curve.
It's an attractive goal, but it has pitfalls.
The Sharpe ratio's pitfalls
- It uses the past. The historical Sharpe doesn't predict the future. An asset with a spectacular Sharpe can have a bad stretch right afterwards.
- It assumes risk is symmetric. Volatility penalizes rises and falls equally, even though nobody minds the rises. That's why it's worth looking at it alongside maximum drawdown and CVaR, which focus on losses.
- It can concentrate too much. The maximum-Sharpe portfolio sometimes puts almost everything in one or two assets that had a good run. Setting a maximum weight per asset usually gives more sensible results.
- It's sensitive to small changes. If expected returns change slightly, the optimal weights can change a lot. That's why the optimizer uses a more robust return estimator than the simple average.
How to use it well
- To compare similar investments over the same period and in the same currency.
- Alongside other metrics: return, volatility, maximum drawdown, VaR and CVaR. The optimizer shows them all.
- By comparing methods: calculate maximum Sharpe, minimum variance, HRP and equal weights side by side with the "Compare methods" option. If maximum Sharpe is only slightly better but much more concentrated, it may not be worth it.
An exercise
- Load the "Global tech" example in the optimizer.
- Calculate with Maximum Sharpe and note the Sharpe and the weights.
- Add a maximum weight of 20% and calculate again.
- Compare with Equal weights.
You'll see how much Sharpe it "costs" to limit concentration. The difference is often small and the constrained portfolio is much more robust.
Sharpe's relatives worth knowing
The Sharpe ratio has a few "cousins" that fix some of its weaknesses:
- Sortino ratio: like Sharpe, but it only counts falls as risk, not rises. It rewards investments that rise strongly but fall little.
- Calmar ratio: compares annual return with the worst drawdown in the period. It's intuitive: how much did I earn for each point of decline I had to endure?
- Information ratio: measures extra return relative to a benchmark index instead of the risk-free rate. It's widely used to evaluate funds that try to beat an index.
None of them is perfect. Looking at several at once gives a fuller picture than relying on just one.
In short
The Sharpe ratio answers a key question: was the risk worth it? It's useful for comparing, but it's built on the past, it treats rises and falls the same, and it can lead to overly concentrated portfolios. Use it as one more piece of the analysis, not the only one.
Try it with your own assets
Build a list and see which portfolio the model calculates, in your currency.
Disclaimer: Educational and simulation tool. It is not investment advice or a personalized recommendation. Past performance does not guarantee future results.