Size it before you risk it.
The first thing a good trader controls isn't the entry — it's the loss. Set your capital, your risk, and your stop, and this tells you exactly how big the position can be across all 11 markets we track.
Educational tool, not advice. It shows how large a position can be for a chosen risk — never whether to take the trade, or in which direction. Contract sizes and leverage caps are broker-typical defaults; confirm yours with your broker.
The one rule this enforces
You decide the most you're willing to lose on a trade — a fixed, small slice of your capital (most professionals cap it near 0.5%). Everything else follows from arithmetic:
risk $ = capital × risk% → notional = risk $ ÷ stop-loss% → margin = notional ÷ leverage
Because the loss you take if you're stopped equals notional × stop-loss%, this single identity sizes every instrument the same way — whether the dollar is the quote currency (Gold, EURUSD, Bitcoin) or the base (USDJPY, USDCAD). We solve it, round the size down to a tradable lot, and never up.
Why it asks how much you keep on the exchange
Holding your whole account inside a broker or exchange is a counterparty risk of its own. A common practice is to keep only 10–20% on the venue and use leverage to carry the same position on that smaller balance.
That's mathematically fine — and quietly dangerous. Your risk budget is measured on your total capital, but a stop-out or a price gap is paid out of the balance that's actually on the exchange. If that balance can't absorb the loss, you get liquidated even though your total capital is healthy. So the calculator adds two guards: it down-sizes if the required margin won't fit, and again if a gap beyond your stop (assumed up to 1.5×) could over-draw the on-exchange balance. The effective leverage figure is the number that actually bites — watch it.
What this is — and isn't
This is education and arithmetic. It tells you how large a position can be for a risk you chose. It does not tell you whether to take the trade, or which direction to go — direction isn't knowable, and anyone who says otherwise is selling something. See our Lab for the receipts, and our Terms for the full disclaimer.