Forex Position Sizing: Balance, Stop Distance, and Risk Percentage
Understand the inputs behind a forex position-size calculation and why deterministic risk controls matter before every trade.
Choose the account risk first
Start with the maximum account amount you are willing to lose if the stop is reached. Many traders express this as a percentage of current balance, but the appropriate limit depends on their own situation.
Measure the actual stop distance
A wider stop creates more loss per unit of position size. Position size must therefore decrease as stop distance grows when account risk stays constant.
Use the broker contract specification
Tick size, tick value, minimum lot and lot step vary by instrument and broker. Exact sizing depends on those values rather than the symbol name alone.
Round down, not up
When the calculated size falls between allowed lot steps, rounding down preserves the intended maximum risk. Rounding up can quietly exceed it.