Position Size Calculator for Prop Firm Challenges
The single most common reason traders fail prop-firm challenges is position-sizing without a formula. This calculator turns sizing from a feeling into a calculation. Enter your account size, the percent you're willing to risk, and your stop-loss distance. Out comes the exact lot size.
Result
Risk amount
USD 1,000
Position size (lots)
5.00
Position size (micro-lots)
500
Educational tool. Verify with your broker's contract specs before placing any trade. Pip values vary by instrument and account currency — for non-USD pairs and exotic instruments, pull the actual pip value from your platform rather than using the default.
How to use it
The default values are set up for a $100,000 FTMO account risking 1% per trade with a 20-pip stop-loss on a major Forex pair (pip value of $10 per standard lot). Replace each input with your own numbers.
The formula
Position size in lots = (Account size × Risk %) / (Stop in pips × Pip value per lot). The math is simple. The discipline of running it for every single trade is what separates traders who pass from traders who blow up.
Why pip value isn't always 10
For a standard lot of EUR/USD with a USD-denominated account, the pip value is $10. For JPY-quoted pairs, it's roughly different — often closer to $9 — because of the quote-currency conversion. For metals, indices, and crypto, pip value varies widely. The reliable move is to pull the actual pip value from your broker's contract specs or platform before placing the trade. The calculator above accepts any pip value you enter.
Recommended risk percentages by phase
- First month of any new account: 0.5%. Smaller-than-comfortable until you have run the strategy live and confirmed it behaves the way it did in backtest.
- After consistent results: up to 1%. Acceptable across most documented strategies with positive expected value.
- Maximum, ever: 2%. Most FTMO daily-loss limits are 5%. Risking 2% per trade means two losing trades approach the daily limit. Three losing trades exceed it. The math leaves no room.
Related reading
- The 5 patterns that fail traders out of challenges — position-sizing without a formula is failure-mode #1.
- Blew your challenge? Run the failure-audit before retaking.
- FTMO Consistency Rule, explained honestly — smaller per-trade sizing flattens your daily distribution.
Past performance does not guarantee future results. Trading carries substantial risk of loss. Free tool — no email required, no upsell.