A prop firm's rulebook is five numbers. Yours can be too.

Strip the marketing off any prop firm evaluation and what is left is short: a maximum drawdown the account may never breach, sometimes a daily loss limit that ends the trading day early, a profit target the account must reach to pass, an evaluation window in trading days, and one more thing that is easy to miss — a decision about what a breach actually does: does the account fail immediately, or does the day simply lock and trading continues tomorrow?

That is the entire object. Feed it, and a trader's trade-by-trade statistics, into a simulator and out comes a probability: the share of simulated paths that reach the target before they breach a floor or run out of days. Nothing about a firm's brand, marketing or reputation enters that arithmetic — only the five numbers and the trades.

Many independent traders already carry a version of that object without calling it one. “I stop for the day after losing two percent.” “I am done trading this account if I am ever ten percent down from my equity high.” “I want to know whether this size survives ninety trading days.” Those sentences are a daily loss stop, a maximum drawdown and an evaluation window — the firm's name is simply the word that is missing.

What is actually missing is not the rule. It is the test. A free calculator that asks “would I pass this firm's challenge” is common. The question “does my own strategy survive the limit I already impose on myself” is asked far less often — yet nothing in the arithmetic changes when the same engine is pointed the other way.

Set a win rate, a reward-to-risk ratio, a risk size and a maximum drawdown — the one rule every account needs — and this runs a seeded Monte Carlo of 200 trades across 4,000 paths, live, in this page. Every number below is recomputed the instant a control moves; nothing here is precomputed or faked.

Illustrative calculator — 4,000 seeded paths, single fixed risk per trade, absorbing breach. The full app runs up to 25,000 paths against your imported trade history, with a daily stop, a goal and a ruin threshold all optional and independently set.

A firm's rulebook earns a trader's attention because it is dated, cited, and simulated before a fee changes hands. A rule a trader writes for themselves is not less real for having no fee attached to it — it is the thing the fee-paying decision is supposed to be a stand-in for in the first place. Running it through the same engine, at the same path count, with the same seeded reproducibility, is not a smaller version of the product. It is the identical computation with one fewer party at the table.

Nothing about that costs extra. The simulator does not know or care whether the numbers it is given came from a firm's published document or from a trader's own stated limits; it resamples trades and checks equity against a floor either way. That symmetry is why modeling a personal rule set is free and full-accuracy by construction, not by discount.

Two assumptions carry the entire result above, and both apply to a personal rule exactly as they apply to a firm's. First, trades are resampled independently and identically from the win-rate and reward-to-risk you set — a losing streak here is coincidence, never a regime, a news shock, or a change in how you are trading. Second, a rule you enter is simulated as obeyed, on every path, without exception. The model has no way to know whether you would actually stop at the floor you typed in — that is a fact about you, not about the arithmetic.

Losses a real account can suffer that this simulation does not model at all include a price gap, a forced liquidation, a broker outage, or slippage beyond a stated cost assumption. None of those are represented here, in the full app, or in any PropSurvival output.

Is modeling my own trading rules really free?
Yes. It runs the same Monte Carlo engine, at the same path count, with no signup, no card, and no gate on accuracy — modeling a rule set you define costs the engine nothing extra to compute over modeling a firm's.

Does this replace a firm evaluation?
No. It answers a different, prior question: whether a rule survives your own trade statistics before any fee — a firm's or otherwise — is involved.

What if I don't have a formal rule yet?
Start with one number. A maximum drawdown is the only required field; every other rule — a daily stop, a goal, a horizon, a ruin threshold — can be explicitly recorded as off rather than left blank.