DanFinPosition Size Calculator
Find the exact forex lot size and units to trade so a single stop-out never risks more than you intend.
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Claim your spot →How it works
The calculator turns a risk rule into an exact forex position size. It takes the amount you are willing to lose, either a percent of your account or a fixed amount, and divides it by your stop-loss distance in pips multiplied by the value of one pip. The result is the number of units to trade, shown as standard, mini and micro lots. Widen the stop and the position shrinks; tighten it and it grows, while the money you risk stays the same.
The value of a pip is not fixed. It depends on the pair you trade and your account currency, so the calculator works it out from the current price you enter. When the pair is already quoted in your account currency no conversion is needed; otherwise the tool converts the pip into your account currency using that price. Correct sizing matters most on a prop firm challenge, where one oversized trade can breach the drawdown limit and end the account. See how your sizing and edge combine into a real pass rate with the prop firm simulator, or find your optimal risk percentage with the Kelly criterion calculator.
Find your optimal risk % →How this tool works
Method, assumptions and limits
This calculator turns three inputs, your account size, the percentage you want to risk, and your stop-loss distance, into an exact position size so a single stop-out loses no more than you planned.
The maths. First it works out the money at risk: account balance × risk percentage. A $100,000 account risking 1% puts $1,000 on the line. It then converts your stop distance into the loss per unit at that stop, using the pair and current price, and divides: position size = risk amount ÷ (stop distance × value per unit). Units are rounded down to a whole step, and lots are units ÷ 100,000 (a standard FX lot).
Worked example. A $100,000 account risking 1% ($1,000) with a 20-pip stop on EUR/USD at roughly $10 per pip per lot: $1,000 ÷ (20 × $10) = 5 standard lots, about 500,000 units, so a full 20-pip stop-out costs close to the planned $1,000.
What it assumes, and does not do. It assumes your stop is filled at the level you set, with no slippage, gapping or spread, and uses the current price for the conversion. It ignores commissions and swap, and it sizes one trade in isolation, so it does not account for several correlated positions open at once. It tells you how to turn a risk you have chosen into a size; it is not advice on how much to risk.
Position sizing: frequently asked questions
How do I calculate my position size?
Work out the amount you are willing to risk, which is your account balance times your risk percentage. Divide that by your stop-loss distance in pips multiplied by the value of one pip. The result is the number of units to trade, which you can express as standard, mini or micro lots.
Why do I enter the current price?
Because the value of a pip depends on the pair's exchange rate and your account currency. The calculator uses the current price to convert your risk into the pair's currency, so the position size is correct for any pair, not only the ones quoted in your account currency.
What is a pip?
A pip is the standard smallest price move for a currency pair. It is 0.0001 for most pairs and 0.01 for pairs quoted in Japanese yen. Your stop-loss distance is measured in these pips.
How does my stop loss change the position size?
They move in opposite directions. A wider stop means a smaller position for the same risk, and a tighter stop allows a larger position. Your risk in money stays fixed; only the size changes.
Why does position sizing matter for a prop firm challenge?
A single oversized trade can breach the drawdown limit and end the challenge instantly. Consistent, correctly sized positions keep each loss small and predictable, which keeps you in the challenge long enough for your edge to play out. See how it affects your odds with the prop firm simulator.
Disclaimer: DanFin is provided for educational and informational purposes only and does not constitute financial, investment, or trading advice, nor a recommendation of any firm, product, or strategy. The simulator and calculators are simplified statistical models based on the figures you enter; their outputs are hypothetical, are not predictions, and do not guarantee future results. Trading leveraged products carries a substantial risk of loss and is not suitable for everyone. Do your own research and consider consulting a licensed professional before making any financial decision. Some links on this site are affiliate links; if you use them, DanFin may earn a commission at no extra cost to you, which never changes the results the tools give you or the content shown.