How the lot size is calculated
The calculator sizes the trade so that a full stop-out — including commission — costs no more than the amount you chose to risk.
The result is rounded down to 0.01 lots, so you never risk more than planned. On gold, 1 lot is usually 100 oz, so a $1.00 move is worth $100 per lot. On forex, a 1-pip move on 1 standard lot is worth $10 on USD-quoted pairs like EURUSD and GBPUSD.
Daily loss room
Most firms measure the daily limit from your balance at server midnight, and count floating losses, commission and swap. If you are already down today, you have less room; if you are up, the room grows.
Max loss room
The calculator uses whichever room is smaller, and tells you how many full stop-outs you can take before either limit is hit.
FAQ
What lot size should I use on a $100k prop account?
Start from risk, not lots. Risking 0.5% ($500) on XAUUSD with a 5.00 stop and $7 commission gives 0.98 lots. The same $500 on EURUSD with a 20-pip stop gives 2.41 lots.
Why include commission?
Commission is charged whether you win or lose, and prop firms count it against your drawdown. On short stops it can be a big share of the loss — a 0.48 stop on gold at 0.1 lots loses $4.80, but $5.90 after a $1.10 commission.
Are the firm presets up to date?
Presets reflect each firm's published standard rules at the time of writing. Rules change and vary by program and account size, so always confirm with your firm and edit the percentages if needed.
What does "safe risk for 3 losses" mean?
It's the largest risk per trade that still lets you lose three times in a row today without breaching the daily limit — a common rule of thumb for prop traders.