Forex Position Size Calculator

A position size calculator reverses the usual question. Instead of choosing a size and hoping the loss is acceptable, you decide the loss first, set the stop where the chart says it belongs, and let the maths choose the size. Enter your balance, the percentage you are willing to risk, the pair and the stop distance in pips.

The position size calculator formula

The pip value per unit is the pip size converted into dollars: 0.0001 for USD-quoted pairs, 0.01 divided by the rate for USD/JPY, and a conversion rate for crosses.

Worked examples

These figures are illustrative.

Most platforms accept sizes in steps of 0.01 lots, so round down rather than up. Rounding 0.1875 up to 0.19 would push the risk slightly above $50.

How to read the result

The lot size is the largest position that keeps a stopped-out trade within your chosen risk, before costs. The spread and any commission add to the loss, and in a fast market a stop can fill beyond its level, so real losses can be larger than planned.

Two habits make the number more useful. First, keep the risk percentage fixed, so a run of losses shrinks your positions automatically. Second, set the stop from the chart, not from the size you would like to trade. The pip calculator shows what each pip is worth at the size you choose, and the margin calculator checks that your account can hold it. For how to place stops on a real chart, see our EUR/USD chart guide.