Lot size and the stop line for the day
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Enter your account size, the risk you take per trade and your stop distance. You get the lot size, the money that ends your trading day, and how many consecutive losses you survive before the daily and overall limits.
Written by someone who passed prop firm challenges three times (twice in 2025, once in 2026) and audited the source code of 15 EAs.
What the numbers mean
- Lot size: the loss you accept per trade, divided by your stop distance
- Stop line for the day: half of the daily limit. The trade taken to win it back is the dangerous one
- Losses until the daily limit: if this is two or three, an ordinary losing streak ends your day
- Losses until the overall limit: how much room the whole challenge has
Start with one number
If you do nothing else today, put your own account size and stop distance in the box above and look at one line: how many losses you survive before the daily limit. Two or three is the answer that ends challenges.
I have been on the wrong side of it. On a demo day where new entries were already blocked, my account still reached −3.11%, because the stops from the previous day were still working.
The three rules I keep
- Risk 0.5–1% of the account per trade
- When the day reaches half of the daily limit, stop trading for the day
- Decide the number of trades per day in advance
Plain, and it is what kept disqualification at 0–1% even when the trade direction was a coin flip across 54 sizing rules and 1,000 runs each.
What this does not tell you
- Whether you will be profitable. This only measures how hard you are to disqualify
- Spread and slippage. Your real loss is slightly larger than the calculation
- Positions carried overnight: their stops count against the next day too
More on that in how daily drawdown is actually counted.
よくある質問
How much should I risk per trade in a prop firm challenge?
I keep it at 0.5-1% of the account. In a test where the trade direction was decided by a coin flip across 54 sizing rules and 1,000 runs each, fixing the risk per trade and the stop-for-the-day kept disqualification at 0-1%.
Is this calculator free?
Yes, and there is no sign-up. Your inputs are stored in your own browser and are never sent to this site.
Does blocking new trades protect the daily limit?
No. Positions carried from the previous day can still hit their stops and count against today.