Your backtest shows one equity curve — one particular order in which your wins and losses happened to fall. Monte-Carlo simulation asks a simple, brutal question: what if that order had been different? Because in live trading, it will be.
The core idea
Take your strategy's trades and reshuffle their sequence thousands of times. Each shuffle is a plausible alternate history with the same trades in a different order. Now you don't have one equity curve — you have a whole distribution of them. That distribution tells you what a typical outcome looks like, not just the lucky one your backtest happened to draw.
What it reveals
- Real drawdown risk — your single backtest might show a 10% max drawdown, but the reshuffles reveal how bad it could plausibly get. That worse number is what you should plan around.
- Risk of ruin — in what fraction of alternate histories does the account blow up or fail a prop-firm rule? If it's not near zero, your sizing is too aggressive.
- Fragility — strategies whose profit depended on one specific run of trades fall apart under reshuffling. That's exactly the kind you want to catch before going live.
Why it matters for prop traders
A trailing drawdown doesn't care that your backtest's losses were conveniently spaced out. Monte-Carlo shows you the clustered-loss versions of your own strategy — the ones that end funded accounts — so you can size for them in advance.
TapeScript runs Monte-Carlo on every strategy as part of its gauntlet, reporting the drawdown distribution and ruin odds alongside the headline curve — so you trade the realistic outcome, not the lucky one. Stress-test your edge →