Position Size Calculator
Find the exact lot size that keeps a losing trade inside your risk budget. Built for prop-firm rules. 1% risk, 5% daily drawdown, and everything around them.
Input
Auto-filled from the selected pair. Override if your broker quotes differently.
Result
Risk Amount
$500.00
1% of $50,000
Standard Lots
1.67
100,000 units each
Mini Lots
16.67
10,000 units each
Micro Lots
166.67
1,000 units each
Units
166,667
Base currency
Prop Firm Tip
Risking 1% or less per trade is ideal for prop firm challenges. You have room for 5+ consecutive losses before hitting a 5% daily drawdown limit.
What Is Position Size?
Position size is how much of an instrument you buy or sell on a single trade, expressed in lots or units. It is decided before entry, from three numbers you already know: your account balance, the percentage of it you are willing to lose on this trade, and the distance in pips between your entry and your stop-loss. Position sizing is the step that converts a percentage you choose into a quantity you can actually place.
The Position Size Formula
Every position size calculator reduces to one expression. The calculator above applies it and converts the result into standard, mini, micro and unit terms.
Position size = (Account balance x Risk %) / (Stop-loss in pips x Pip value)
The numerator is your risk budget in currency: what you lose if the stop is hit. The denominator is what a one-unit move costs you across that stop distance. Dividing one by the other gives the largest size whose worst case still equals the budget you set. Widen the stop and the size falls; that relationship is the whole mechanism.
A Worked Example
On a 50,000 account risking 1% per trade, the risk budget is 500. With a 30-pip stop on EUR/USD at a pip value of 10 per standard lot, the denominator is 300, so the position is 1.67 standard lots. Halve the stop to 15 pips and the same 500 budget supports 3.33 lots. Neither version risks more than the other. Only the size changed, because the distance to invalidation changed.
Position Sizing on a Challenge Account
On a FundedFast challenge or funded account, both of which are simulated trading accounts, the maximum daily loss is 5% of your starting balance and the maximum total loss is 10% of your starting balance, raised to 20% where the drawdown add-on was purchased on an eligible account. Both are fixed thresholds set against the starting balance rather than trailing your peak equity. The practical consequence is arithmetic: at 1% risk per trade a full stop-out uses a fifth of the daily allowance, while at 3% it uses more than half, and two of them end the day.
Why Spread and Commission Belong in the Calculation
Spread and commission are paid whether the trade wins or loses, so a stop placed at exactly your risk budget is breached slightly before price reaches it. The advanced settings above fold both into the result. The effect grows as the stop tightens: on a 5-pip stop a 1-pip spread is a fifth of the distance, while on a 50-pip stop it is a fiftieth. Orders also fill at the price the market gives you, so a stop-loss defines intended risk rather than guaranteeing it.
This section is educational information about how position sizing interacts with loss limits on a simulated evaluation account. It is not financial advice and not a recommendation to take any position.
Position Size Calculator FAQ
How do you calculate position size in forex?
Multiply your account balance by the percentage you are risking to get a risk budget in currency, then divide that budget by your stop-loss distance in pips multiplied by the pip value of the instrument. The result is the position size that loses exactly your budget if the stop is hit.
What percentage should I risk per trade?
There is no universally correct number, and it depends on your strategy and the rules of the account you trade. What is arithmetic rather than opinion is the consequence: on an account with a 5% daily loss limit, 1% per trade leaves room for five full stop-outs in a day, while 3% leaves room for one. Lower risk per trade buys more consecutive losses before a limit is reached.
What is pip value and why does the calculator ask for it?
Pip value is what a one-pip move is worth on one standard lot of the pair you are trading, in your account currency. It varies by pair and by account currency, which is why the same stop distance produces a different position size on EUR/USD than on USD/JPY. The calculator pre-fills a typical value per pair and lets you override it.
Does a wider stop-loss mean I should trade smaller?
Yes, if the risk budget stays fixed. Stop distance sits in the denominator of the formula, so doubling it halves the position size. That is what keeps the currency amount at risk constant across setups with different invalidation distances, rather than the size staying constant and the risk moving.
Should spread and commission be included?
They should, because both are paid regardless of outcome and both eat into the distance between entry and stop. The advanced settings fold them into the result. The tighter the stop, the larger the proportion they represent, which is why scalping strategies are more sensitive to them than swing strategies.
Is position size the same as lot size?
They are related but not identical. Position size is the risk decision, expressed as the quantity that puts a chosen percentage of the account at stake. Lot size is the unit that quantity is expressed in, where one standard lot is 100,000 units, a mini lot is 10,000 and a micro lot is 1,000. This calculator returns the position size and then converts it into each lot unit.
How does position sizing affect a prop firm challenge?
It determines how many losing trades an account survives. With a 5% daily loss limit, risking 1% per trade means five consecutive full stop-outs reach the limit, while 3% means two do. Sizing is the main variable a trader controls in that calculation, since the limit itself is fixed. Confirm the limits that apply to your own account before sizing to them.
Is this calculator free to use?
Yes. It is free and does not require an account. Nothing you enter is stored or sent anywhere; the calculation runs entirely in your browser.