Sharpe Ratio
Also known as: risk-adjusted return, sharpe, reward-to-variability ratio
What is it?
The Sharpe Ratio measures how much return a strategy earned for the amount of bumpiness it put you through, so two strategies can be judged on more than their headline gains. You take the average return, subtract the risk-free rate (what you could have earned holding something safe like a short-term government bill), and divide that by the standard deviation of the returns, which is just a number describing how much those returns jumped around from month to month. A higher Sharpe means more return per unit of total volatility, so a smoother equity curve scores better than a jumpy one that ended at the same place.
| Same 2% risk-free rate | Strategy A (smooth) | Strategy B (jumpy) |
|---|---|---|
| Headline return | 18% / yr | 22% / yr |
| Return above risk-free | 18% - 2% = 16% | 22% - 2% = 20% |
| Std dev of returns (the wobble) | 12% — calmer ride | 28% — wild swings |
| Sharpe = excess / std dev | 16 / 12 ≈ 1.33 | 20 / 28 ≈ 0.71 |
| Verdict (historical, past data) | Better risk-adjusted winner | Bigger headline, worse per unit of risk |
For example, suppose Strategy A returned 18 percent a year and Strategy B returned 22 percent, and the risk-free rate is 2 percent. If A's returns wobbled with a standard deviation of 12 percent it scores about 1.33, while B's wobble of 28 percent gives it about 0.71, so the lower-headline strategy is actually the better risk-adjusted performer because it delivered nearly the same edge with far less stomach-churning swing. The common pitfall is judging a strategy by its biggest year or its raw return and ignoring the path it took to get there, because a high return built on wild swings can wipe out an account during a bad stretch before the long-run average ever arrives.
As a rough industry feel, a Sharpe above 1 is generally considered solid and above 2 strong, but these figures are historical and computed on past data. Past performance does not guarantee future results, no strategy is risk-free, and your capital is at risk on every trade.
Why it matters: It lets you compare strategies on both return and smoothness at once, so you stop being seduced by a big headline number that hides punishing volatility.
Sharpe Ratio = (average return - risk-free rate) / standard deviation of returns
The Sharpe Ratio is a core lens for ranking strategies because it weighs return against the volatility you must endure to capture it.
Real-world example
A strategy averaging 18 percent against a 2 percent risk-free rate with a 12 percent standard deviation scores about 1.33, beating a 22 percent strategy whose 28 percent swings drop it to about 0.71.
How SignalBots handles it
Where SignalBots reports a Sharpe Ratio for a strategy it is a historical estimate from past data shown alongside drawdown and a /risk-warning link, helping you compare signals on the Web Dashboard rather than chasing the loudest headline return.
Pro tip
Annualise the inputs consistently and compare strategies over the same period; a Sharpe from monthly data is not comparable to one from daily data unless both are scaled the same way.
Common pitfalls
Chasing the highest raw return and ignoring the volatility behind it, then getting shaken out during the drawdown that the smooth Sharpe winner would have avoided.
Frequently asked questions
What is a good Sharpe Ratio?
As a rough guide, above 1 is generally considered solid and above 2 is strong, but these are historical conventions, not targets. The figure depends entirely on past data and never guarantees future results.
What is the risk-free rate in the formula?
It is the return you could earn on a very safe asset like a short-term government bill, used as the baseline you should beat before taking on any risk. Subtracting it isolates the extra return your strategy earned for accepting volatility.
Why divide by standard deviation?
Standard deviation measures how much the returns swung around their average, so dividing by it rewards a smooth equity curve and penalises a jumpy one. Two strategies with the same return get different scores based on how wild the ride was.
Can the Sharpe Ratio be negative?
Yes, if the average return falls below the risk-free rate the numerator turns negative, meaning you took on volatility and were not even paid the safe baseline for it. A negative Sharpe is a clear sign the strategy underperformed on a risk-adjusted basis in that sample.
What are the limits of the Sharpe Ratio?
It treats upside and downside volatility the same, so it can penalise a strategy for large winning swings, and it assumes returns are fairly normal, which strategies with rare large losses are not. Pair it with drawdown and downside-focused measures like Sortino for a fuller picture.
Trading involves substantial risk of loss. Historical and backtested results do not guarantee future performance. Read the full risk warning.