Metrics6 min read

Maximum Drawdown

Maximum drawdown is the largest peak-to-trough decline in portfolio value over a given period. It measures the worst-case loss you would have experienced if you had entered at the worst possible time and exited at the worst possible moment. It is the risk metric that most directly matches what a real trader experiences.

The formula

MDD = max over time t of (Peak(t) − Trough(t)) / Peak(t)

Where Peak(t) is the maximum portfolio value from the start to time t, and Trough(t) is the minimum portfolio value from the peak forward. Maximum drawdown is always expressed as a percentage of the peak value, so a portfolio that falls from $100,000 to $70,000 has a drawdown of 30%.

Why drawdown matters more than volatility

Volatility is symmetric — it measures both up and down moves equally. A strategy that is volatile but consistently rising looks bad by volatility but is profitable. Drawdown is explicitly one-sided: it captures the actual capital loss a trader would face.

Psychologically, drawdown is also what drives strategy abandonment. A trader experiencing a 30% drawdown doesn't care that the Sharpe ratio is 1.2. They are watching their account lose money and questioning whether the strategy is broken. Most systematic strategies are abandoned during drawdowns — often just before recovery.

Backtested maximum drawdown almost always understates live drawdown. Historical data was selected because it exists — survivorship bias means you're not backtesting through company failures, flash crashes on the exchanges you trade, or the specific combination of conditions that would have caused your strategy to fail. Assume live MDD will be 1.5× to 2× backtested MDD when sizing positions.

Duration is as important as depth

A 20% drawdown that lasts 2 weeks is psychologically and practically very different from a 20% drawdown that lasts 18 months. The duration of the maximum drawdown period tells you how long you would need to hold through a losing stretch before returning to new highs.

Strategies with short, shallow drawdowns and quick recoveries are easier to hold through than strategies with long, grinding drawdowns — even if the depth is the same. Always look at drawdown duration alongside depth.

The Calmar ratio

The Calmar ratio relates annual return to maximum drawdown:

Calmar = CAGR / |Maximum Drawdown|

A Calmar ratio above 0.5 is reasonable. Above 1.0 is strong. Trend-following strategies often have Calmars in the 0.3–0.7 range due to their characteristic long, shallow drawdown periods. Mean-reversion strategies can achieve higher Calmars but are more susceptible to sudden large drawdowns.

Recovery factor

The recovery factor is the total return divided by the maximum drawdown. It answers the question: for every dollar lost in the worst drawdown, how many dollars did the strategy ultimately earn? A recovery factor below 1 means the total profit doesn't cover the maximum loss observed — the strategy may not be worth the risk.

Position sizing implications

Maximum drawdown is the primary input to position sizing under Kelly Criterion variants and fixed fractional methods. If your strategy has a 30% maximum drawdown and you allocate 20% of your total capital, your maximum account drawdown is 6%. Understanding the relationship between strategy MDD and portfolio MDD is essential before live trading.

A common rule: your maximum tolerable account drawdown divided by your strategy's expected MDD (using the backtested figure × 1.5–2 as a buffer) gives you the maximum allocation fraction. Overallocating is the single most common reason traders abandon sound strategies.