How do I calculate lot size for gold?

Divide the cash you are willing to risk by the stop distance in dollars per ounce multiplied by 100 ounces. £100 of risk with a $5.00 stop is 0.20 lots.

How much margin does a gold trade need?

Margin is notional exposure divided by leverage. At $4,600 gold, 0.20 lots is $92,000 notional, needing $4,600 at the 1:20 retail cap.

Should the spread be included in the stop distance?

Yes. The spread is paid in the same dollars per ounce as the loss, so a $5.00 stop with a 30-cent spread is really $5.30 of risk.

What risk percentage is sensible on XAUUSD?

Most professional desks work between 0.25% and 1% per trade. Ten losses at 1% costs about 9.6% of the account; at 3% about 26%.

Gold Position Size Calculator for XAUUSD Risk

Cash risk is balance multiplied by risk percentage, risk per lot is the entry to stop distance multiplied by one hundred ounces, and lot size is the first divided by the second.

The result is rounded down to the nearest hundredth of a lot, because rounding up quietly breaks the risk limit you just set.