Is your Sharpe lying? What Sortino tells you that Sharpe hides.

Sharpe is often the most discussed metric by systematic PMs. It is a useful number with one specific blind spot that Sortino addresses; the difference between the two tells you something material about your return distribution.

What is the difference between Sharpe and Sortino?

The Sharpe ratio is excess return divided by total volatility. Total volatility means standard deviation of all returns, up and down.

The Sortino ratio is excess return divided by downside volatility only. Downside volatility means standard deviation of returns below some threshold (usually zero or the risk-free rate).

Why does the distinction matter?

Sharpe penalises upside volatility as if it were the same problem as downside volatility. It is not. A strategy that has a few big winning months alongside its losing months gets punished by Sharpe for the winners' contribution to total variance. Sortino does not.

When return distributions are symmetric, Sortino and Sharpe will rank strategies similarly. Sortino is approximately √2 times Sharpe.

Take my own live portfolio that runs at Darwinex as a case study: over the past 13 months, it has clocked a Sharpe of 4.12, and its Sortino is 5.70, showing that mathematically the system's day-to-day volatility is heavily driven by positive, right-skewed breakout extensions rather than toxic tail risk.

What happens with positively skewed returns?

When return distributions are positively skewed (occasional big winners against more modest losers, the classic trend-following profile), Sortino looks much better than Sharpe. Trend strategies that win in tail events and bleed slowly in trendless regimes are systematically underrated by Sharpe.

What about negatively skewed returns?

When return distributions are negatively skewed (rare large losers against consistent small winners, the classic vol-selling profile), Sortino and Sharpe diverge in the opposite direction. Vol-selling strategies usually look great on Sharpe and are punishing on Sortino once you include the rare blow-up months.

If your Sortino is materially lower than your Sharpe, you're running a strategy whose tail risk isn't priced into the strategy metrics.

How should allocators interpret the gap?

Sortino > √2 × Sharpe: positively skewed. You are being underrated by the headline Sharpe.

Sortino ≈ √2 × Sharpe: symmetric. Either metric tells the same story.

Sortino < √2 × Sharpe: negatively skewed.

The Calmar ratio (return divided by max drawdown) gets at the same idea from a different angle. Calmar above 1.0 is a useful floor for emerging-manager allocator conversations. Sortino above 2.0 is a useful floor on the variance side. Allocators also stress-test recovery time before they stress-test depth, which is why time-under-water belongs alongside these ratios in monthly reporting.

Why should you present the full triple?

The full triple (Sharpe, Sortino, Calmar) presented together gives the allocator everything they need to characterise the distribution. Presenting only Sharpe signals you either do not know about the others or are hoping the allocator does not ask.

To any systematic traders early in the build: do not be scared of these metrics. Build the portfolio properly and the numbers settle where they should.