Why position size matters

Your position size decides how much money every pip is worth. Get it wrong and a normal price swing can do serious damage. Get it right and every loss is small and planned.

The formula

Lots = amount at risk ÷ (stop loss in pips × pip value per lot)

where amount at risk = account balance × risk %.

Example 1: EUR/USD on a USD account

  • Balance: $2,000, risk 1% → $20 at risk
  • Stop loss: 40 pips
  • Pip value per standard lot on EUR/USD: $10

$20 ÷ (40 × $10) = 0.05 lots

Example 2: USD/JPY on a USD account

For yen pairs, pip value per lot depends on the current price: 100,000 × 0.01 ÷ price.

  • Price 150.00 → pip value per lot ≈ $6.67
  • Balance $2,000, risk 1% = $20, stop 30 pips

$20 ÷ (30 × $6.67) ≈ 0.10 lots

Example 3: wider stop, smaller position

Same $2,000 account, 1% risk, but the chart suggests an 80-pip stop on EUR/USD.

$20 ÷ (80 × $10) = 0.025, rounded down to 0.02 lots.

A wider stop does not mean more risk; it means a smaller position.

Common mistakes

  • Choosing the lot size first and then placing a tight stop to "fit".
  • Forgetting that pip values differ between pairs.
  • Rounding position size up instead of down.
  • Risking a percentage of an amount you have not actually deposited.