Max drawdown: the backtest number that predicts whether you'll quit

Ask a new trader to judge a backtest and they look at the return. Ask a professional and they look at the max drawdown first. The reason is simple and a little uncomfortable: returns are what a strategy promises, but drawdown is what decides whether you are still in the trade to collect. The best strategy you abandon at the bottom is worth less than a mediocre one you actually hold.

What max drawdown measures

Maximum drawdown is the largest peak-to-trough decline in account equity over the test period, expressed as a percentage. If equity climbs to 100, falls to 72, then recovers, the max drawdown is 28%. It is the worst it got — the deepest hole the strategy dug before climbing out. Crucially it is a path statistic, not an endpoint one: two strategies can finish at the same return with completely different drawdowns, and the one with the shallower drawdown is the better business.

Depth is half the story — duration is the other half

Everyone quotes drawdown depth. Far fewer quote drawdown duration — how long the account stayed below its previous high. A 20% drawdown that recovers in three weeks is an annoyance. A 20% drawdown that grinds sideways and down for eleven months is an ordeal, and it is the duration, not the depth, that breaks people's discipline. They watch a flat-to-bleeding equity curve for months, conclude the strategy is dead, and switch it off — often right before it recovers.

Why backtested drawdown is the optimistic case

Here is the trap. The backtested max drawdown is the worst drawdown on the one historical path you happened to test. The live future will hand you a different path, and there is no reason it will be kinder. In fact, because you likely selected this strategy partly because its backtest looked smooth, the backtested drawdown is biased low. Plan for a live drawdown meaningfully worse than the backtest — a Monte Carlo simulation will quantify how much worse by showing the 95th-percentile drawdown across thousands of resampled paths.

Sizing positions around drawdown

Drawdown is not just a metric to read — it is the input to position sizing. Work backwards. Decide the largest account drawdown you can tolerate without interfering — be honest, most people overestimate this. Take the strategy's Monte Carlo 95th-percentile drawdown. The ratio between your tolerance and that figure tells you how much of your capital this strategy should run. If the strategy's stress-case drawdown is 40% and your real tolerance is 20%, you trade it at half size — or you do not trade it.

1. Find the strategy's stress-case drawdown — the Monte Carlo p95, not the single backtest number.
2. Decide your true tolerance — the loss you can watch without flipping the switch.
3. Scale allocation so the stress-case drawdown stays inside your tolerance.
4. Re-check after every regime change — drawdown profiles drift as markets change.

Noon Barbari reports max drawdown and drawdown duration on every backtest, and the Monte Carlo page gives you the distribution of drawdowns — including the p95 you should actually size against — across 1,000+ resampled paths. The free tier includes both.

Returns win the marketing. Drawdown wins or loses the actual game, because it determines whether you are still holding the strategy at the moment it would have paid you back. Read it first, size for the stress case, and you remove the most common reason retail systems fail — the trader, not the strategy, giving up.