Forex Max Lot Size Calculator
Trade right up to what's left of your risk budget without going over it. Enter the amount you have left before you hit your own daily or weekly loss limit and your stop, and get the largest lot size that keeps a single trade inside it.
Cash left before you hit your daily, weekly, or per-account loss limit.
How much of that remaining budget to risk on one trade.
Distance from entry to your stop, measured in pips.
Value of one pip per standard lot ($10 for most USD-quoted pairs).
Risking $2,500.00 on a 20-pip stop, the largest trade that stays inside your budget is 12.50 standard lots.
For educational purposes only. Read our risk warning before trading.
How the Max Lot Size Is Calculated
Start from the cash you can afford to lose: your remaining risk budget times the fraction of it you'll risk on this trade. Divide that by the cost of your stop — the stop distance in pips multiplied by the pip value of one standard lot — and you get the largest lot size that keeps the loss inside your budget.
Sizing to Your Risk Budget
| Concept | What it means |
|---|---|
| Size to your budget | Risk a fraction of what's left of your loss limit, not your full account balance — that remaining budget is what actually stops you out. |
| Wider stop | A wider stop costs more per lot, so the same budget buys you a smaller maximum lot size. |
| Keep a buffer | Never risk 100% of your budget on one trade — one stop-out at the limit ends the session with no margin for error. |
Frequently Asked Questions
Whatever loss limit you actually trade against — a personal daily or weekly stop, the cushion left on a prop firm's drawdown rule, or simply the amount you have decided you can afford to lose this session. The cash left before that limit is the real cap on how much a single trade can cost you, and this tool sizes your position so that even a full stop-out stays inside it.
No. Risking 100% of what's left on one trade means a single loss ends the session. Most traders risk a small fraction so a losing run still leaves room to recover. Keep the fraction conservative and treat the figure here as the absolute ceiling, not a target.
It is the cash a one-pip move is worth on a single standard lot. For most USD-quoted pairs like EUR/USD that's about $10. JPY and cross pairs differ, so check your broker's contract specs and enter that exact figure for an accurate lot size.
Yes — it works for a personal account or a prop firm's funded account alike, because you enter your own remaining budget. If you trade under a firm's rules, find the smaller of the daily and overall drawdown cushions first and enter that as your budget; for a personal account, enter whatever loss limit you actually hold yourself to.
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