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Sharpe Ratio

The Sharpe ratio measures risk-adjusted returns — how much excess return you earn per unit of risk. A higher Sharpe ratio means better compensation for the risk taken.

Formula

Sharpe Ratio = (Portfolio Return - Risk-Free Rate) ÷ Portfolio Standard Deviation

Example

Portfolio return 12%, risk-free rate 5%, standard deviation 15%. Sharpe = (12% - 5%) ÷ 15% = 0.47. A Sharpe above 1.0 is good; above 2.0 is excellent.

How to Interpret It

Sharpe helps compare investments with different risk levels. A 20% return with 30% volatility (Sharpe 0.5) is worse than a 12% return with 10% volatility (Sharpe 0.7). Always consider risk-adjusted returns.

Real-World Sharpe Ratios

InvestmentSharpe RatioPeriod
S&P 500 (1Y)1.87Through late 2025
S&P 500 (long-term avg)0.5–0.9620+ year average
S&P 500 (6-month rolling)2.0–3.0Peak in Nov 2025
Walmart (WMT)5.042025 screening
Typical hedge fund0.5–1.0Long-term average

Benchmark: Sharpe <1.0 is sub-par, >1.0 is good, >2.0 is strong, and >3.0 is exceptional. The S&P 500's long-term Sharpe around 0.5–0.96 means most diversified portfolios should aim to exceed 1.0 through asset allocation.

Worked Example: Comparing Two Portfolios

Portfolio A: 18% return, 25% std dev, risk-free 5% → Sharpe = (18% - 5%) ÷ 25% = 0.52

Portfolio B: 12% return, 10% std dev, risk-free 5% → Sharpe = (12% - 5%) ÷ 10% = 0.70

Portfolio B has a lower return but a higher Sharpe ratio — it delivers more return per unit of risk. For most investors, Portfolio B is the better choice.

💡 Pro Tip: Sharpe's Blind Spot

The Sharpe ratio treats upside and downside volatility equally. A stock that swings wildly upward gets penalized the same as one that swings wildly downward. For a more nuanced view, use the Sortino ratio, which only penalizes downside deviation.

Common Mistakes

1. Using too short a time period. A 3-month Sharpe ratio is nearly meaningless. Use at least 3 years of data — ideally 5+ years to capture a full market cycle.

2. Comparing across different asset classes blindly. A bond fund's Sharpe of 1.2 isn't automatically better than a stock fund's 0.8. They serve different portfolio roles. Compare within the same category.

3. Ignoring non-normal distributions. Sharpe assumes returns follow a bell curve. Strategies with fat tails (like options selling) can show great Sharpe ratios until a black swan event wipes out years of gains.

4. Cherry-picking the risk-free rate. Using a 1% T-bill rate instead of the current ~5% makes any portfolio look better. Always use the prevailing risk-free rate for an honest comparison.

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Frequently Asked Questions

What is a good Sharpe ratio?

Generally: below 0.5 is poor, 0.5-1.0 is acceptable, 1.0-2.0 is good, and above 2.0 is excellent. The S&P 500 historically has a Sharpe ratio around 0.5-0.6. Hedge funds often target 1.0+. Keep in mind that very high Sharpe ratios (3+) over short periods often indicate unsustainable strategies or data mining.

Can a negative Sharpe ratio be good?

No. A negative Sharpe means the investment earned less than the risk-free rate. While you could argue a -0.1 Sharpe is "less bad" than a -0.5 Sharpe, the interpretation breaks down with negative values. In practice, a negative Sharpe signals the investment isn't compensating for its risk.

Sharpe ratio vs. Sortino ratio?

The Sortino ratio only considers downside volatility, ignoring upside swings. This makes it better for evaluating strategies with asymmetric returns (like options). If a strategy has frequent small gains and rare large losses, the Sharpe ratio may look great while the Sortino reveals hidden tail risk.

Related Terms

Pe Ratio Eps Beta Roi Dividend Yield Market Cap Roe Cagr

Real-World Example To understand the Sharpe Ratio, consider an investor choosing between two mutual funds with different risk profiles. Fund A is a conservative government bond fund that returned 4% over the last year with very little fluctuation. Fund B is a volatile technology stock fund that also returned 4%. While the nominal returns are identical, the risk is vastly different. By calculating the Sharpe Ratio—which divides excess return by the standard deviation of returns—investors can quantify the difference. Fund A has a high Sharpe Ratio because it achieved that return with minimal risk. Fund B has a low or negative Sharpe Ratio because its high volatility suggests the 4% return was achieved by taking significant, potentially dangerous risks that could easily turn negative. In this real-world scenario, the ratio tells the investor that Fund A is the superior choice, as it provides a safer path to the same destination. This illustrates how the metric helps separate "lucky" returns from genuine skill, ensuring that an investor is compensated fairly for the risks they actually took.

Common Mistakes A major mistake investors make is relying on the Sharpe Ratio as a guarantee of future performance. Because the ratio is calculated using historical data, it cannot predict how a portfolio will behave in a new economic environment or during a market crash. Another frequent error is assuming that returns are normally distributed. The Sharpe Ratio assumes a symmetrical bell curve of returns, but financial markets often have "fat tails," meaning extreme losses occur more often than standard math predicts. This can make the ratio look deceptively high during stable periods while failing to warn of potential catastrophic drops. Additionally, investors often ignore the impact of leverage. Adding debt to a portfolio can artificially inflate the Sharpe Ratio by boosting returns, while the underlying risk increases exponentially. Finally, comparing Sharpe Ratios across different asset classes can be misleading because the "risk" measured in one sector (like credit risk) does not always correlate with the risk in another (like liquidity risk).

Comparison with Related Metrics While the Sharpe Ratio is the industry standard, it is often compared to other metrics to better suit specific investment goals. The Sortino Ratio is a common alternative that differs by looking only at downside volatility. Since investors generally dislike downside risk but are often indifferent to upside volatility, the Sortino Ratio is often considered a more accurate measure of risk-adjusted performance for non-symmetric returns. Another related metric is the Treynor Ratio, which uses beta (systematic market risk) instead of standard deviation. This makes the Treynor Ratio more appropriate for diversified portfolios where unsystematic risk has been eliminated. Additionally, the Calmar Ratio compares returns to the maximum drawdown (the largest peak-to-trough decline) to emphasize survival. While the Sharpe Ratio provides a broad overview of risk and return, the Sortino Ratio is often preferred for individual assets, the Treynor Ratio for diversified funds, and the Calmar Ratio for long-term value investing strategies focused on avoiding ruin.