Sizing trades inside prop firm drawdown limits
· 7 min read
A funded account has a second constraint that a personal account does not: a hard loss limit that ends the account when it is breached. Sizing has to respect the limit you are closest to, not the one you like better.
The two limits
Prop firms impose a daily loss limit, typically 4% or 5% of the balance, and an overall limit, usually 8% to 12%. The daily one resets each session. The overall one does not — it is a floor for the life of the account.
That difference is the whole game. Losing 4% today may be perfectly legal, and it also spends nearly half of an 8% overall allowance permanently. Traders fail challenges by treating the daily limit as the budget and discovering the overall one only when it stops them.
The tighter limit governs
Before sizing a trade, work out both remaining amounts and take the smaller. If your daily allowance has 400 USD left but your overall allowance only has 150 USD left, then 150 is what you have, and a trade risking 200 is not viable no matter how good it looks.
The calculator does this comparison for you when you fill in the prop firm section: enter your two limits as percentages and how much you have already lost today and in total, and it reports what is genuinely left, how many losing trades of the current size fit inside it, and the largest lot size that stays within it.
Read the drawdown type in your rules
Firms measure the overall limit in three different ways, and they behave very differently.
- Static — the floor is fixed at the starting balance minus the allowance. Profits build a genuine buffer above it.
- Trailing on balance — the floor follows your closed-trade high water mark upward, and never comes back down. Profits do not accumulate as protection.
- Trailing on equity — the floor follows your peak equity, including unrealised profit. An open trade that runs up and gives it back can breach the account without a single losing trade being closed.
Under equity trailing, letting a winner retrace is not merely disappointing, it is dangerous. Check which type applies before you size anything, because the same 2% risk means different things under each.
Practical habits that keep challenges alive
Risk less than the rules allow. If the daily limit is 5%, sizing at 0.5% per trade means ten consecutive losses are needed to reach it, which converts a single bad session from fatal to merely annoying.
Count correlated positions as one. Three dollar-negative trades at 1% each is a 3% bet, and a daily limit does not care that you opened them separately.
Know when your firm's day rolls over, since it is usually a specific broker-server time rather than your local midnight, and a trade held across that boundary belongs to a different day than you think.
Leave the last slice of the daily allowance untouched. Reaching exactly 5.0% when the limit is 5% is a breach, and slippage on a stop is enough to get there from what looked like a safe 4.8%.
Frequently asked questions
What percentage should I risk on a prop firm challenge?
Well below what the rules permit — somewhere between 0.25% and 1% per trade is common among traders who pass consistently. The profit target is reached by a handful of good trades, not by sizing aggressively, and the limits punish variance far more than they reward speed.
Does the daily limit reset if I am in profit?
The allowance resets each day, but usually against the balance at the start of that day, so profits made today may not extend today's room. The overall limit never resets. Read how your firm defines the daily baseline, because some measure from the previous day's closing balance and others from peak equity.
Do open positions count towards the drawdown?
At most firms, yes: the limits are evaluated on equity, which includes floating losses. A position sitting in drawdown can breach the account before you close it, which is why sizing has to be based on the stop distance and not on hoping it comes back.
Educational tool. Check the size in your platform before trading; leveraged trading carries a risk of loss.