Position size calculator
A position size calculator answers the question traders most often skip: how big should this trade be? Rather than choosing a lot size and hoping, you fix the amount you are willing to lose if the stop-loss is hit, and the calculator finds the size that matches.
The position size formula
Units = risk amount ÷ (stop distance in pips × pip value per unit in USD)
Lots = units ÷ 100,000 (or ÷ 100 for gold)
Worked examples
EUR/USD: balance $10,000, risk 1%, stop 25 pips. The risk amount is $100. A pip is worth $0.0001 per unit, so 25 pips is $0.0025 per unit. $100 ÷ $0.0025 = 40,000 units, which is 0.40 lots.
USD/JPY at 150.00: balance $10,000, risk 1.5%, stop 40 pips. The risk amount is $150. A pip per unit is 0.01 yen, worth 0.01 ÷ 150 dollars. Forty pips per unit is therefore 0.4 ÷ 150 ≈ $0.00267. $150 ÷ 0.00267 gives about 56,250 units, or 0.5625 lots. Most platforms trade in steps of 0.01 lots, so you would round down to 0.56 lots to stay within the planned risk.
These examples use round, illustrative numbers.
Reading the position size calculator result
- Round down, not up. Rounding up means risking slightly more than planned on every trade.
- The stop comes first. Place the stop where the trade idea is wrong, then let the calculator set the size. Tightening the stop to fit a bigger position defeats the purpose.
- Costs are extra. Spread, commission and slippage add to the real loss. A stop can also fill at a worse price in a gap.
- Check the margin. A correctly sized trade can still need more collateral than you have available; confirm with the margin calculator.
Keeping risk to a small, fixed share of the balance means a run of losing trades reduces the account gradually rather than ending it. The pip calculator shows the per-pip value behind these numbers.