Forex Position Size Calculator (AUD)

How to use this calculator

Enter the account balance and currency, the percentage of the account to risk if the stop is hit, the stop-loss distance in pips, and the pair. The calculator returns the position size in standard lots and units, the pip value at that size, and the exact dollars at risk. Sizes round down to the 0.01-lot step brokers actually accept, so the risk figure never exceeds the limit and you are not left wondering whether a fractional lot will be rejected.

The stop distance is the input traders most often guess, and it is the one I would call the most consequential. Measure it from entry to the invalidation level the analysis provides, then let the position size absorb the difference. A wider stop with a smaller position risks the same dollars as a tight stop with a larger one.

The position sizing formula

Lots = (balance x risk % / 100) / (stop-loss pips x pip value of 1.00 lot). The pip value term converts the pair's quote currency into the account currency, which is why the same trade sizes differently in AUD and USD accounts and why a lot size cannot be copied from one account currency to another without adjusting it. Our pip value calculator shows that conversion on its own.

Every part of this formula is observable before the trade: balance from the account, risk percentage from the plan, stop distance from the analysis, pip value from current exchange rates. Nothing in it predicts the market; it only fixes the cost of being wrong, and that is the trade-off I would accept every time.

Why risk percentage beats fixed lots

Trading a fixed lot size means risk per trade drifts as your balance changes and as you switch pairs with different pip values. A percentage rule is essential because it scales both ways: losses shrink the next position, wins grow it, and the account compounds without any single trade being able to do outsized damage. Ten consecutive 1% losses leave about 90% of the account intact; ten fixed-size losses on an oversized lot can halve it.

The percentage rule is also what makes performance comparable across pairs. A 25-pip stop on AUD/USD and a 40-pip stop on GBP/JPY carry the same dollar risk once the position is sized to the stop, so your win rate and average return stop depending on which pair was traded. New traders can start with the framework in our beginner forex broker guide.

Stop-loss distance and volatility

Stops placed inside a pair's normal hourly range get hit by noise rather than by being wrong. Volatile pairs and news sessions need wider stops, which the formula automatically compensates for with a smaller position. The common failure is the reverse: keeping the position size fixed and tightening the stop to force the maths, which converts one planned loss into several unplanned ones and is what I cannot get past when I see a trader blaming the pair for a string of small losses.

Position sizing also interacts with leverage limits. The size this calculator returns still has to fit within the margin, which ASIC caps at 30:1 on major pairs for retail accounts, a cap David Levy verified against the ASIC instrument; the leverage guide explains the caps and our margin calculator shows the margin a given size requires. I would always check the margin after sizing, because ASIC's 30:1 cap can bite. If the required margin exceeds free equity, the constraint that binds is margin, not risk, and the position must shrink to fit both.