Sharpe ratio intuition for retail

Return per unit of risk

Sharpe ratio is the most common way to measure risk-adjusted return. The formula: Sharpe equals your return minus the risk-free rate, divided by the standard deviation of your returns. In plain English: how much return did you earn for each unit of volatility you took? Higher is better.

Walk through it. Say your monthly returns average 2 percent. The risk-free rate is about 0.4 percent monthly. Excess return is 1.6 percent. The standard deviation of your monthly returns, a measure of how wobbly the equity curve is, comes to about 2 percent. Sharpe = 1.6 / 2.0 = 0.8. Below 1, meaning the smoothness of your returns is not quite worth the size of them.

Now compare two traders. Trader A returns 20 percent a year with smooth, low-volatility monthly results. Trader B also returns 20 percent a year but the curve is wild, with months of plus 10 and minus 8. Same annual return. Very different experiences and very different Sharpe. A might have a Sharpe of 1.5; B might have 0.4. The number tells you which one you can actually live with, and which one might wipe you out via path before the year ends.

For retail traders, Sharpe is a sanity check, not a goal. Two cautions. First, on a small sample like 30 trades, the number is noisy and you should not over-interpret it. Second, Sharpe penalizes upside and downside volatility equally, which can flag good systems as risky just because they have occasional big winners. Use Sharpe as one input. Use drawdown and expectancy as the others.

Recap: Sharpe = (return - risk-free) / volatility. Above 1 decent, above 2 great, above 3 rare. Smooth curves score higher than wild ones with the same returns.