Gold lot size from the stop distance: why a wider stop means a smaller position
Many traders choose a lot size by feel: a bigger lot when a setup looks convincing, a smaller one when it does not. On gold this habit is expensive, because the distance to a sensible stop changes a lot from day to day. The same lot can risk 50 dollars on a quiet morning and 400 dollars after a news release.
Working the lot size out from the stop distance keeps the risk of each trade the same, whatever the market is doing.
The basic sum
On most MetaTrader 5 gold contracts, 1.00 lot is 100 ounces, so a move of 1 dollar in the price is 100 dollars per lot. Check the contract size in your own terminal (Symbol specification), because brokers differ.
The sum is:
lot = money you accept to lose on this trade / (stop distance in dollars x dollars per 1.00 lot per 1 dollar move)
Example with a 100-ounce contract and 200 dollars of risk:
- stop 4 dollars away: 200 / (4 x 100) = 0.50 lot
- stop 8 dollars away: 200 / (8 x 100) = 0.25 lot
- stop 16 dollars away: 200 / (16 x 100) = 0.125, rounded down to 0.12 lot
The risk stays at roughly 200 dollars in all three cases. Only the lot changes.
Why the stop comes first
The stop belongs where the trade idea is clearly wrong, for example beyond the last swing high or low. Moving the stop closer just to fit a bigger lot puts it inside normal noise, and it gets hit for no reason. Decide the stop from the chart first, then let the sum give you the lot.
Three details that change the result
- Round down, never up. Brokers have a minimum lot step, often 0.01. Rounding up adds risk you did not plan.
- Spread and slippage. Around big releases the fill can be several dollars worse than the stop price. Some traders add that distance to the stop before doing the sum, or stay out of the market at those times.
- Account currency. If your account is not in US dollars, convert the dollar risk at the current rate.
How this fits a prop-firm daily limit
On a challenge or funded account the daily loss limit is the hard boundary. If each trade risks a fixed amount, you can count in advance how many losing trades in a row the day can absorb before the limit is reached, and stop before that point.
Where a daily lock fits in
The sum keeps each trade the same size in risk. A second safeguard is a daily stop that actually prevents new trades. Our free MetaTrader 5 utility, Spectar Daily Loss Limiter, stops trading for the rest of the day once today's loss reaches the figure you set, counting the day from the broker's server midnight and including floating losses.
Free on the MQL5 Market: https://www.mql5.com/en/market/product/200369
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