Drawdown is the distance between your equity's most recent peak and its current value. Maximum drawdown is the deepest such valley in the whole record. It is the single most consequential number in any backtest — more than return, more than win rate — because it measures the experience of holding the strategy, not just the destination.
The arithmetic is brutal and asymmetric
A 10% drawdown needs an 11% gain to recover. A 30% drawdown needs 43%. A 50% drawdown needs a full 100% — you must double your remaining capital just to get back to even. This asymmetry is why professional risk management obsesses over the depth of losses rather than the height of gains: losses compound against you at an accelerating rate.
Duration matters as much as depth. A 15% drawdown recovered in three weeks is a very different psychological event from the same 15% ground out over eleven months. Most people can tolerate sharp pain; almost no one tolerates long, grinding doubt. When you read a backtest, look for the longest stretch between equity peaks — that is the period your discipline would have been tested daily.
Reading drawdown in a backtest
First, assume the future will be worse. Your historical max drawdown is the best case, because the future contains regimes your test window didn't. A common professional heuristic is to plan for one and a half to two times the backtested maximum.
Second, ask what drove it. One catastrophic trade points to a risk-control gap (position too large, stop too wide, or no stop at all). A long sequence of ordinary losses points to a regime mismatch — the strategy kept firing in conditions it wasn't built for. The fixes are completely different.
Third, run sequence stress-tests. The order of trades in your backtest is one draw from a distribution. Reshuffle the same trades a few hundred times — a Monte Carlo simulation — and watch how deep the drawdowns get across resamples. If a plausible reordering ruins the account, the strategy's size is wrong even if its logic is right.
Designing for survivable drawdown
Decide your maximum acceptable drawdown before designing the strategy, then let it dictate position size — not the other way around. Add a circuit breaker that halts trading at a defined equity loss. And remember why any of this matters: the goal of risk management is not to maximize the backtest, it is to guarantee you are still present, solvent and psychologically intact for the strategy's good periods. Educational research only — no risk framework eliminates the possibility of loss.