What is a “safe” blow rate for a prop firm account?

A blow rate is simple to define and hard to measure. It is the percentage of account lifetimes that end in a breach of the firm’s maximum drawdown rule. If a strategy has a 6% annual blow rate, it means that out of many simulated years of trading the same rules on the same account, roughly six in a hundred ended with the account blown.

Most traders never calculate this. They look at win rate and profit factor, pass one challenge, and assume the approach is sound. But win rate tells you nothing about tail risk. A strategy can win 90% of trades and still blow an account if the 10% of losses cluster badly. Blow rate is the only metric that directly answers the question that matters: will this survive?

Why win rate and profit factor hide the real risk

Profit factor measures gross profit against gross loss. It is a quality signal, not a survival signal. Two strategies with an identical profit factor of 2.8 can have wildly different blow rates depending on how their losses are sequenced and how aggressively the position is sized against the drawdown floor.

This is the core failure mode in prop trading. People size for the median outcome — the comfortable middle of the distribution — and then get knocked out by a sequence that lives in the bad tail. The median says you make money. The tail says you lose the account. Both are true at once.

What counts as safe

There is no universal threshold, but a useful working rule for evaluation accounts is this: an annualized blow rate above 15% is fragile, and anything in double digits deserves scrutiny. At Puravida Edge we treat 15% as a hard ceiling — no published portfolio variant is allowed to exceed it. That is a design constraint, not a marketing line.

Notice the spread. The two forex portfolios sit near 0.4% — effectively bulletproof over the modeled horizon — while the 100K Aggressive variant runs at 14.47%, deliberately close to the ceiling in exchange for a higher median return. That is the trade-off made explicit: you do not get the higher number for free, you pay for it in tail risk.

How to estimate your own

You cannot read blow rate off a single backtest equity curve, because one curve is one sequence of trades. The real distribution of outcomes only appears when you reshuffle the trade sequence thousands of times and watch how often the drawdown floor gets touched. That is what Monte Carlo simulation is for — and it is the subject of the next article in this series.