Guide · 2 min read
How to calculate lot size for gold (XAUUSD) on MT5
Short answer: Decide how much money you will lose if the stop is hit. Measure the stop distance in dollars. Multiply that distance by the contract size (usually 100 ounces) to get the loss per lot. Divide your risk by the loss per lot. The answer is your lot size, rounded down.
Published: 24 October 2026.
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Most traders pick a lot size first and a stop second. That is backwards. The stop goes where the trade idea is wrong. The lot size is what makes that stop cost a fixed amount of money.
The formula
- Risk in moneyAccount balance times the share you risk (for example 1%).
- Stop distanceEntry price minus stop price, in dollars.
- Loss per lotStop distance times the contract size.
- Lot sizeRisk in money divided by loss per lot.
A worked example
Say the account holds 10,000 dollars and you risk 1%. That is 100 dollars.
You buy gold with a stop 5 dollars below the entry. With a 100-ounce contract, the loss per lot is 5 times 100, so 500 dollars.
100 divided by 500 is 0.20. You trade 0.20 lots. If the stop is hit, you lose about 100 dollars, plus costs.
Same account, same risk, but the stop is 12.50 dollars away. The loss per lot is 1,250 dollars, and 100 divided by 1,250 is 0.08 lots. A wider stop means a smaller position, not a bigger loss.
Check the contract size first
The formula only works with the right contract size. Most MT5 brokers use 100 ounces per lot for XAUUSD, but not all of them. In MetaTrader, right-click the symbol in Market Watch, open Specification and read the contract size. Our contract calculator shows what one lot moves per dollar for the common markets.
Mistakes that make the risk bigger than planned
- Using a fixed lot size for every trade, so wide stops lose far more than tight ones.
- Forgetting the spread and commission. Add them to the stop distance.
- Rounding up. Round the lot size down to the broker's lot step.
- Using the account's own currency as if it were dollars. Convert the risk first.
- Moving the stop further away after entry, which quietly doubles the risk.
Use the calculator
Our free position size calculator does this sum for you and shows how many losses in a row your daily and maximum loss limits can take. If you are setting rules for yourself, the trading plan builder writes them out in money amounts.
The Monthly Pass and the Lifetime Pass are software licences for your own MetaTrader account. They score every robot and strategy you run the same way, with costs inside every number. See the plans.
FAQ
What is the formula for gold lot size?
Lots = money you risk divided by (stop distance in dollars times the contract size). With the usual contract of 100 ounces, a 1 dollar move is worth 100 dollars per lot, so a 5 dollar stop costs 500 dollars per lot.
How many ounces is one lot of gold on MT5?
On most MT5 brokers one standard lot of XAUUSD is 100 troy ounces. Some brokers use 10 ounces or 1 ounce. Check the contract size in the symbol's specification before you trade.
How much is a 1 dollar move in gold worth?
With a 100-ounce contract, a 1 dollar move is 100 dollars per lot, 10 dollars per 0.10 lot and 1 dollar per 0.01 lot.
Should I risk the same lot size on every trade?
No. Keep the risk in money the same and let the lot size change with the stop distance. A wider stop means a smaller lot, so every loss costs about the same.
Does the spread change the lot size?
It should. The spread, commission and any slippage add to the real loss when a stop is hit. Add them to the stop distance, or the true risk is bigger than planned.
What if my account is not in US dollars?
Gold is priced in dollars, so the loss per lot is in dollars too. Convert your risk amount into dollars at today's rate first, then use the formula.
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