Contents
The formula
Lots = (account risk in currency) divided by (stop distance in points multiplied by value per point per lot). That is the whole formula. The value per point per lot for XAUUSD on a standard account is $1 per point per lot, so a 500-point stop risks $500 per lot. If your account is $10,000 and you want to risk 1 percent, that is $100, so you trade 0.20 lots. If the same trade has a 200-point stop, the same $100 risk means 0.50 lots.
That is the correct behaviour, and it is the part most calculators get wrong. Position size is a function of the stop, not a function of confidence. A setup with a wider stop gets a smaller size. A setup with a tighter stop gets a larger one. The risk in currency stays constant, which is the entire point.
We have a full treatment of the underlying concepts in position sizing for gold, and the specific tool is covered in the gold lot size calculator.
Why the ruin maths matters
The reason to size at 1 percent rather than 5 percent is not conservatism, it is arithmetic. A trader risking 5 percent per trade needs a 40 percent win rate just to break even before costs. A trader risking 1 percent can sustain a 25 percent win rate indefinitely. Most people who blow accounts do not have a bad strategy, they have a good strategy with a ruinous size.
Here is the part that surprises people. Even with excellent execution, a losing streak of seven or eight trades at 5 percent takes you down 28 to 33 percent, and you then need roughly a 42 percent gain just to get back to where you started. At 1 percent, an eight-trade losing streak costs about 8 percent, and recovery is roughly 8.7 percent. The difference in recovery difficulty is the whole argument.
There is also the psychological component. A 33 percent drawdown makes most traders change strategy, which is exactly the wrong response, because their strategy was not the thing that was broken. Trading discipline covers how to keep a tested process intact through a drawdown, and risk of ruin for gold traders has the full maths.
The volatility adjustment most people skip
A fixed 1 percent is a good default, but it over-risks quiet conditions and under-risks violent ones. The refinement is to scale the risk with recent realised volatility, so that a trade taken during a 40-point daily range is sized smaller than one taken during a 200-point day.
The practical implementation is simple. Measure the average true range on your trading timeframe, compare it to a recent baseline, and scale the percentage proportionally. If the current ATR is double the baseline, halve the percentage. This is usually the difference between a trader who survives a volatility event and one who does not.
The other side of the same coin is the stop. If the market has expanded, a stop placed at the usual distance is likely to be hit by noise, and the correct response is either a wider stop with a proportionally smaller size, or no trade. The rule is that the stop goes where the thesis is wrong, never where the size would be comfortable.
The mistakes that break the maths
The first is moving the stop. A stop widened after entry is a larger loss than planned, and it breaks the fixed-fractional property that makes the strategy survivable. If the stop needs to be somewhere else, the trade should not have been taken. We cover this in stop loss placement for gold.
The second is adding to a loser, which increases the risk on precisely the trade the system has told you is wrong. Averaging down converts a small, controlled loss into an uncontrolled one.
The third is sizing by account balance at the start of the month and not updating. If the account grew 20 percent, the next trade should risk 1 percent of the new balance, not the old one. This is a small rule with a large compounding effect, and it is discussed in fixed fractional position sizing.
The fourth is ignoring correlated exposure. Two gold trades, one long and one short, on different timeframes, are not two independent risks. If the second is a hedge of the first, the net risk is not 2 percent. Portfolio diversification for gold traders covers how to count correlated risk properly.
A worked example
Account: $10,000. Risk rule: 1 percent, so $100 per trade. Current gold price: 3,400. You are considering a long entry at 3,400 with a stop at 3,350, which is 500 points away. At $1 per point per lot, one lot risks $500, so the size is 100 divided by 500, which is 0.20 lots.
Now the volatility check. The daily ATR is 60 points, versus a 30-point baseline, so volatility is double normal. Scale the risk down by half, giving $50, and the position becomes 0.10 lots.
Now check the margin requirement. At 0.10 lots with typical 1:500 leverage, margin is around $68, which is comfortable against a $10,000 balance. If the margin were uncomfortably high, the correct response is to find a different setup with a tighter stop, not to exceed the risk limit.
That is the complete process, and it takes under a minute once it is a habit.