Position size calculator
This position size calculator works backwards. Instead of choosing a lot size and hoping the loss is acceptable, you decide the loss first, as a percentage of your account, and the calculator finds the position that matches your stop-loss distance.
The formula
Position size (units) = money at risk ÷ (stop distance in pips × pip value per unit)
Lots = units ÷ 100,000
For a USD-quoted pair such as EUR/USD, the pip value per unit is 0.0001 dollars, so one standard lot has a pip value of $10.
Worked example (illustrative)
Account balance $8,000; risk 1.5% per trade; EUR/USD with a 30-pip stop.
- Money at risk: $8,000 × 1.5% = $120.
- Required pip value: $120 ÷ 30 pips = $4 per pip.
- Lot size: $4 ÷ $10 per pip per lot = 0.4 lots (40,000 units).
If the stop were 60 pips instead, the same $120 would allow only 0.2 lots. A wider stop means a smaller position, not a bigger loss.
How to read the result
The output is the largest position that keeps the loss at your stop within your chosen percentage. Round down to the lot increment your platform allows, never up. Then check that the margin required is available using the margin calculator; a position can be correctly sized for risk and still need more collateral than you want to commit.
Three limits apply. First, the stop may fill at a worse price in a gap or fast market, so the actual loss can exceed the plan. Second, spread and commission are not included; subtract them from your risk budget if they are significant. Third, several open positions in related pairs (for example EUR/USD and GBP/USD) behave partly like one larger position, so combined risk can exceed the per-trade figure.
Many traders use a fixed small percentage per trade because it keeps a losing streak survivable. That is a risk-control habit, not a promise of profit. For the pip arithmetic behind the calculation, see the pip value calculator.