Prop Firms and Evaluation Rules

A proprietary trading firm offers to fund you. You pay a fee, trade a simulated account under a set of rules, and if you pass you trade the firm's capital for a share of the profit. The model is legitimate, widely used, and structured in a way most applicants misread — they optimise for the profit target when the rule that fails them is almost always the drawdown limit.

How an evaluation is structured

Details vary between firms; the shape is consistent. A typical two-stage evaluation on a $100,000 simulated account:

Read past the headline numbers to two details that decide everything. Is the drawdown measured from the starting balance or from the highest balance reached? A trailing drawdown that follows your equity up is a much harder rule. And is it measured on closed trades or on equity including open positions? An equity-based rule can be breached by an open position that later recovers.

Daily loss limits are the hard part

The profit target is a number you reach over dozens of trades. The daily limit is a number you can hit in an afternoon, and it does not care that the rest of the month was fine.

At 2% risk, three ordinary consecutive losses end the evaluation. Track 5's streak arithmetic says a 40% win-rate method produces a run of three regularly — so the applicant risking 2% is not taking a small chance of failing, they are relying on not meeting an event their own win rate makes common.

The total limit, measured properly

Run the risk-of-ruin model with the loss level set to the firm's 10% rule, over the 60 trades a realistic evaluation takes, with a genuine 40% win rate at 2:1:

The second column is the fixed-drawdown rule; the third is the trailing version, and the difference between them is the single most important thing in this lesson. Under a trailing rule at 2% risk, a trader with a real edge fails five times out of six.

Sizing for the rule, not the target

The correct approach inverts the instinct. Size from the constraint, and let the target take as long as it takes.

1. Work out the per-trade risk that survives your expected losing streak inside the daily limit. If your streak is four and the limit is 5%, that is 1.25% at most — and less, to leave room.
2. Check it against the total limit with the model above. If the breach probability is above 10%, size down again.
3. Compute how many trades the target then needs. At 1% risk with a +0.2R expectancy, 8% takes about 40 trades. At 0.5% it takes 80.
4. Accept the trade count. Forty trades at a sane size beats twenty at a size that fails one time in three.

Rules that catch people out

• Daily limits reset on the firm's clock, not yours — often 5pm New York. A position held across that boundary spans two days' limits.
• News restrictions. Some firms prohibit holding through high-impact releases. Track 4's calendar lesson becomes a compliance requirement.
• Consistency rules. Several firms void a pass where one day produced too large a share of the profit, which penalises exactly the lumpy result a large winner produces.
• Weekend holding, prohibited at some firms.
• Maximum lot size, which can quietly make your normal sizing impossible.

The economics of the fee

Treat an evaluation as a purchase with an expected value, and the decision becomes arithmetic rather than aspiration.

• Your realistic pass probability is the ruin model above, not the firm's advertised pass rate.
• The fee is spent whether or not you pass, and refunds usually come with the first payout rather than on passing.
• Repeated attempts compound the cost. Three attempts at $500 is $1,500 spent before any profit.
• Funded accounts have the same rules, so passing is not the end of the drawdown constraint — it is the start of living under it with real money attached.

When it makes sense

1. You have 100+ live trades with a measured expectancy and a known worst drawdown. Without those, the pass probability is unknowable and the fee is a lottery ticket.
2. Your worst historical drawdown is well inside the firm's limit — comfortably under half of it, not just under it.
3. You can trade the same way under the rules, including any news and consistency restrictions.
4. The fee is affordable if lost, because on the numbers above it frequently will be.

Where those four hold, an evaluation is a reasonable way to trade size you do not have. Where they do not, it is a paid attempt to discover whether you have an edge — and the answer is available for free, from a hundred trades at minimum size on your own account.