The formula before the order
Risk amount = equity × risk percentage. Lots = risk amount ÷ (stop distance in pips × pip value for one lot). With USD 1,000 and 1%, the loss budget is USD 10. If the stop is 25 pips and one pip is worth USD 10 for a standard lot on that instrument, raw size is 10 ÷ 250 = 0.04 lots. Then round down to the broker volume step.
Why pip value changes
Pip value depends on contract size, pair and account currency. For a USD-quoted pair such as EURUSD, a standard lot is often USD 10 per pip; USDJPY or a differently denominated account requires conversion. Gold, crypto and indices have their own contract sizes, so never automatically apply the EURUSD value to XAUUSD.
Include spread, commission and slippage
Actual loss can exceed the theoretical calculation when execution crosses the stop, especially during a release or thin market. Allow for spread and fees, then round size down. Available margin and leverage determine whether an order can open; they do not reduce the economic risk of price movement.
Add portfolio risk
Two correlated positions are not independent. An EURUSD BUY and USDJPY SELL may both expose the account to a weaker dollar. Calculate total loss if all stops are hit and reduce each size when setups share a currency or market driver.
FAQ
Must I always risk exactly 1%?
No. One percent is a prudent ceiling; lower risk may be more appropriate.
Can I calculate size without a stop?
No: without an invalidation distance, maximum loss is undefined.