Prop Firm Drawdown Calculator

The formulas

static floor = start × (1 − maxDD)
trailing floor = equity high − start × maxDD
max risk to survive N losses = 1 − (floor ÷ equity)^1/N

The daily floor is today's starting balance minus the daily loss allowance (daily% × account size, the convention most firms use; some compute it on the day's starting equity instead, which is why both inputs are separate). Your effective breach level is whichever floor is higher, that is the one you hit first on the way down, and the calculator flags which constraint is binding right now.

Survivable consecutive losses assume fixed-fractional sizing: each loss multiplies equity by (1 − risk), so the streak that breaches is the smallest n with equity × (1 − risk)ⁿ at or below the floor, n = ln(floor/equity) ÷ ln(1 − risk). The inverse of that formula answers the more useful planning question: given the streak length you want to survive, what is the biggest risk per trade you can afford?

A worked example

Take a $100,000 evaluation with a 10% trailing max drawdown, and suppose you have run the account up to a $104,000 equity high before pulling back to $101,000. Static would leave the floor at $90,000; trailing puts it at 104,000 − 10,000 = $94,000. Your room is $7,000 (6.9% of current equity), not the 10% printed in the rules. At 1% fixed-fractional risk that room absorbs seven consecutive losses (101,000 × 0.99⁷ ≈ $94,139, still above the floor; the eighth loss breaches at ≈ $93,197). To guarantee surviving ten straight losses you would need to cut risk to 1 − (94,000/101,000)^1/10 ≈ 0.72% per trade. This is the arithmetic that makes trailing drawdown the silent killer of funded accounts: profit you give back moves both sides of the equation against you.

And on most days none of that is your real constraint. With a 5% daily limit measured from a $101,000 day start, today's floor is $96,000, higher than the trailing floor, so the daily rule binds first. Traders who plan only around the max drawdown routinely fail on a daily breach with the "big" cushion untouched.

Why trailing rules punish scaling up

Under a static rule, early profit is a genuine cushion: every dollar earned is a dollar further from the floor. Under a trailing rule, early profit converts one-for-one into floor height until the limit locks (if it ever does). The practical consequence is that risk per trade should be at its smallest right after a new equity high under a trailing rule, exactly when overconfidence says to size up. Running your own numbers here after each trading day, thirty seconds of admin, keeps the floor visible while it moves. Pair it with therisk-of-ruin simulatorto see how often your strategy's losing streaks reach the lengths that matter, and with theprofit target calculatorto see the pass probability these constraints leave you.