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). USD/XXX pairs like USDJPY, crosses, indices and non-USD accounts vary with the exchange rate or your broker's contract — use the custom pip value for precision (USDJPY: 1,000 ¥ ÷ the USDJPY rate; ECB reference rates of 2 October 2026 put it at 157.67, verified 5 October 2026).
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 the 5% daily limit of FTMO's 2-Step Challenge (or right at the 3% limit of the 1-Step) 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
In FTMO's 1-Step Challenge, your best day cannot exceed 50% of your positive days' profit (Best Day Rule) — a direct argument for the same fixed risk percentage on every trade instead of doubling up when you feel confident. Pick one number here and leave it alone.
Daily loss limits (5% and 3%), the equity definition and the Best Day Rule: FTMO trading objectives (verified 5 October 2026).
Automating it
With SignalForge you pick the position size type in your dashboard (fixed, risk % or the signal's lot); with risk % and an alert without a lot field, the EA sizes each MT5 order with this same math from the stop you send in sl (fields in the docs). On prop-firm accounts, Prop Firm Shield (Trader plan and up) watches the daily loss and the profit target and closes positions when they are hit — the part no calculator can do for you at 3 a.m. It does not enforce the firm's max drawdown. Test your alert format in the webhook tester or read the 4-step setup guide.
FAQ
THE THREE SIZING QUESTIONS THAT COME UP ON A FUNDED ACCOUNT.
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.
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SignalForge AI is an order-execution tool. We do not provide investment advice. Trading involves risk of loss. This calculator is for information only.