Sharpe Ratio — What is the Sharpe Coefficient?

What is the Sharpe Ratio?

The Sharpe Ratio (Sharpe coefficient) is a measure of risk-adjusted return. It tells you how much additional return you get for each unit of risk you take.

Created by William Sharpe (Nobel Prize winner in Economics) in 1966.

Formula

Sharpe Ratio = (Rp - Rf) / σp

Where:

• Rp — average portfolio return
• Rf — risk-free rate (e.g., Polish government bond yields)
• σp — standard deviation of returns (volatility)

Example

Portfolio A: 12% return, 15% volatility, 4% risk-free rate

Sharpe = (12% - 4%) / 15% = 0.53

Portfolio B: 8% return, 5% volatility, 4% risk-free rate

Sharpe = (8% - 4%) / 5% = 0.80

Portfolio B has a better Sharpe Ratio — despite lower return, it gives more per unit of risk.

Value Interpretation

Historically, the S&P 500 has a Sharpe Ratio of around 0.4–0.6 in the long term.

What is it used for?

• Comparing funds/ETFs — which gives better risk-adjusted return?
• Strategy evaluation — does adding a new asset improve portfolio Sharpe?
• Backtesting — key metric when testing historical strategies.

Limitations

1. Assumes normal return distribution — in reality, markets have "fat tails" (black swans).
2. Treats upward and downward volatility equally — large gains "penalize" Sharpe Ratio, though investors enjoy them.
3. Time period dependent — Sharpe Ratio for 1 year vs 10 years can differ drastically.
4. Risk-free rate changes — in zero interest rate era (2020–2021), Sharpe was artificially inflated.

Alternatives

• Sortino Ratio — like Sharpe, but only measures "downside" volatility (downside deviation). Better measure for investors who only care about losses.
• Calmar Ratio — return divided by maximum drawdown.

How can Freenance help?

Freenance shows key portfolio metrics, helping evaluate whether your investments provide adequate return for risk taken. Compare results with benchmarks and optimize allocation.

👉 Analyze your portfolio — freenance.io