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Position Size Calculator
Get the position size — the lot size that caps your loss at the amount you choose — from your balance, risk percent and stop in pips. The formula is shown, and it rounds down to your broker's lot step so the risk never runs over.
Position size is the lot size that risks no more than a set amount if your stop is hit. In lots it is (account balance × risk%) ÷ (stop-loss in pips × pip value per lot). On a $10,000 account risking 2% with a 50-pip stop and a $10 pip value, that is 200 ÷ 500 = 0.4 standard lots. Always round down to your broker's lot step so the actual risk never exceeds your plan.
Your risk
Position to take
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How it works
What position sizing does
Position sizing flips the usual question around. Instead of guessing a lot size and seeing what happens, you fix the most you will lose on the trade and let the math return the size that produces exactly that risk. It is the single biggest lever a trader controls.
The formula
risk amount = account balance × (risk% / 100)
lots = risk amount ÷ (stop-loss in pips × pip value per lot)
The pip value per lot must already be in your account currency. For most USD-quoted pairs on a USD account that is $10 per standard lot; for cross pairs, get the exact figure from the Pip Value Calculator first.
How to use this calculator
- Enter your account balance and the percentage you are willing to risk on this trade.
- Enter the distance from entry to stop-loss, in pips.
- Enter the pip value per standard lot in your account currency.
- Set your broker's smallest lot step — the result is rounded down to it.
Worked example 1 — the 2% rule
A $10,000 account risking 2% can lose $200. With a 50-pip stop and a $10 pip value, the per-lot risk is 50 × 10 = $500, so 200 / 500 = 0.4 standard lots (40,000 units). If price hits the stop, the loss is the planned $200.
Worked example 2 — a smaller account
A $5,000 account risking 1.5% can lose $75. With a 25-pip stop and a $10 pip value, per-lot risk is $250, so 75 / 250 = 0.30 lots. Tightening the stop to 25 pips lets you trade a larger size for the same dollar risk.
When position sizing matters
It matters most when your stop distance changes from trade to trade. A fixed lot size means a tight-stop trade and a wide-stop trade carry very different dollar risk; sizing from risk keeps every loss the same size, which is what makes a strategy's expectancy meaningful.
Common mistakes
- Rounding up. Rounding the lot size up pushes your real risk above plan. This tool always rounds down to your lot step.
- Using the wrong pip value. On a cross-currency account the pip value is not $10 — compute it first, otherwise the size is wrong.
- Ignoring spread and slippage. Your real loss is the stop distance plus spread and any slippage; size with a small buffer if your stop is tight.
Frequently asked questions
How do I calculate forex position size from risk percent?
(balance × risk%) ÷ (stop pips × pip value).