Lot size calculator for MT5.
Balance, risk and stop distance in — position size out. Flip on prop-firm mode and it also checks your sizing against an FTMO-style daily loss limit, so one bad cluster of trades cannot end your challenge. No signup, nothing leaves your browser.
Formula: lots = (balance × risk%) / (stop-loss pips × pip value per lot). Round down to your broker's lot step (usually 0.01). JPY pairs and non-USD accounts vary with exchange rates — use the custom pip value for precision.
How to use it (and why the prop-firm check matters)
The classic formula answers one question: how many lots can I trade so that my stop loss costs exactly my chosen risk? With $100,000, 1% risk and a 20-pip stop on EURUSD: $1,000 / (20 × $10) = 5.00 lots. That is correct — and still not safe on a prop-firm account.
Prop-firm daily limits are measured on equity across all open positions at once. Three trades at 1% each, all underwater in the same dollar-correlated move, is a 3% floating drawdown — deep into a 5% FTMO daily limit (or past a 3% 1-Step limit) before a single stop fires. Prop-firm mode divides a buffered daily limit (80% of the firm's, leaving room for spread spikes) across your maximum simultaneous trades and warns you when your per-trade risk exceeds it. The full rulebook, verified against FTMO's own pages, is in our FTMO rules guide for EA traders.
Sizing consistency is also a rule now
FTMO's Best Day Rule fails you if a single day makes over 50% of your positive-day profits — a direct argument for the same fixed risk percentage on every trade instead of doubling up when you feel confident. Pick one number here, put it in your alerts, leave it alone.
Automating it
If your TradingView alerts carry a risk parameter (like risk=1), SignalForge sizes each MT5 order server-side with this same math — and Prop Firm Shield enforces the daily and total equity limits automatically, which is the part no calculator can do for you at 3 a.m. Test your alert format in the webhook tester or read the 4-step setup guide.
FAQ
What lot size for a $100,000 FTMO account?
At 1% risk and a 20-pip stop on a USD-quoted major: 5.00 lots. But check prop-firm mode: with 3 simultaneous trades against a 5% daily limit, keep per-trade risk near 1.3% or below — at 3% per trade you can breach the daily limit with open floating losses alone.
Does this work for gold (XAUUSD)?
Yes — with the 0.1-pip convention, one pip on 1.00 lot of gold is $10, same math as EURUSD. Just make sure your stop distance is counted in 0.1 increments (a $2.00 move = 20 pips).
Why round down and not to the nearest?
Rounding up increases risk beyond what you chose; rounding down keeps you inside it. Brokers step lots at 0.01, so 5.278 becomes 5.27.