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Create AccountPosition Size Calculator
Turn a stop loss and a risk limit into the exact position size, in lots and in units.
Your Result
The calculation runs in your browser. Rates used for currency conversion are indicative — check your broker for the exact figure.
Most traders pick a lot size first and put the stop wherever looks reasonable afterwards. That produces a different loss on every trade — one costs $40, the next costs $380 — and makes it impossible to tell whether a strategy works, because the results are noise.
This calculator reverses the order. You decide what the trade is allowed to cost, you place the stop where the idea is proven wrong, and the size falls out of those two numbers. Size becomes an output rather than a guess.
When to use it
- Before every entry, once the stop has a home.
- When the stop has to be wider than usual — the size should shrink to match.
- On a prop firm challenge, where one oversized trade can breach a daily loss limit.
- After a change in balance, so risk stays proportional as the account moves.
Two steps. First the money, then the size that loses exactly that money at the stop.
Risk Amount = Balance × Risk %
Position Size = Risk Amount ÷ (Stop in Pips × Pip Value per Lot)- Widening the stop shrinks the size. The planned loss has not changed, so the position must.
- Pip value is converted into your account currency before the division, which is why a non-USD account gives a different answer for the same inputs.
- The result is rounded down to two decimals. Rounding up would put you slightly over your risk limit.
A trader with $10,000 risks 1% and needs a 40 pip stop on EUR/USD.
Working: $100 ÷ (40 × $10) = 0.25 lots. If the stop is hit the loss is $100, exactly as planned. Double the stop to 80 pips and the size halves to 0.125 lots — because the loss you accepted has not moved.
What risk percentage should I use?
Most written risk plans sit between 0.5% and 2% per trade. Funded and prop accounts usually need the lower end, because a daily loss limit can be breached by two or three ordinary losses in a row.
Should I include the spread?
The calculation uses the stop distance alone. If your broker charges a wide spread or a round-turn commission, either subtract it from the risk amount first or add a few pips to the stop.
What is the difference between this and a lot size calculator?
Nothing, mathematically. Position size is the general term and includes the unit count; lot size is the same figure expressed only in lots. Use whichever label your platform uses.
My broker will not accept the size it gave me.
Brokers enforce a minimum step, usually 0.01 lots. Round down to the nearest step your platform accepts — rounding up puts you over the risk you agreed to.
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