The Sharpe ratio measures risk-adjusted return by dividing excess return (above the risk-free rate) by the standard deviation of returns. The Sortino ratio improves on Sharpe by penalising only downside deviation, recognising that upside volatility is desirable. Both ratios help traders compare strategies on a level playing field and identify which approaches deliver the best returns for their level of risk.
Sharpe ratio equals excess return divided by total standard deviation of returns. Sortino ratio equals excess return divided by downside standard deviation only. A Sharpe above one is generally considered acceptable, above two is very good. Sortino is preferred for strategies with asymmetric return profiles, such as trend following. Both ratios are annualised for comparison across different time horizons. Neither ratio captures tail risk or maximum drawdown, so they should be used alongside other metrics.
Use Sharpe and Sortino ratios during strategy development to evaluate edge quality. Compare ratios across different parameter settings to find robust configurations. A rising Sharpe ratio during walk-forward testing suggests genuine edge. Allocate more capital to strategies with higher risk-adjusted returns.
Reduce allocation if the rolling Sharpe ratio drops below a pre-defined threshold. Halt a strategy if the Sortino ratio turns negative over a meaningful sample size. Compare live performance ratios to backtested expectations — significant degradation signals regime change. Review and potentially retire strategies with persistently declining ratios.
Weekly, Monthly, Quarterly review periods
A high Sharpe ratio from backtesting does not guarantee future performance — always verify with out-of-sample and walk-forward testing. The Sortino ratio is generally more useful for traders because it does not penalise large winning trades. Aim for a Sortino ratio of at least one point five for any strategy you intend to trade with meaningful capital.
Correlation-aware allocation goes beyond simple diversification by mathematically measuring how assets move together and sizing positions accordingly. Two highly correlated positions (e.g., ES and NQ) effectively concentrate risk. By adjusting allocation based on measured correlations, traders build portfolios with better risk-adjusted returns.
Fixed-fractional position sizing risks a fixed percentage of your account on every trade (commonly 1-2%). This ensures that a string of losses reduces position sizes proportionally, protecting capital during drawdowns. It's the most widely recommended position sizing method for discretionary traders because it's simple, sustainable, and mathematically sound.
A maximum drawdown limit is a predefined loss threshold that triggers mandatory action — reducing size, stopping trading, or reviewing strategy. Common limits: daily max loss (e.g., 3%), weekly max loss (e.g., 5%), monthly max loss (e.g., 10%), and total max drawdown (e.g., 20%). Professional trading firms and prop firms enforce strict drawdown rules.
Portfolio diversification reduces risk by spreading capital across multiple uncorrelated or negatively correlated assets, strategies, and timeframes. True diversification requires correlation analysis — holding 10 tech stocks is not diversified. The goal is to generate returns from multiple independent sources rather than relying on a single trade or strategy.