How can I calculate the margin?
Margin calculation formula for forex instruments is the following:
(Lots * contract size / leverage) where the result is at always in the primary currency of the symbol.
For STANDARD accounts all forex instruments have a contract size of 100 000 units. For MICRO accounts all forex instruments have a contract size of 1 000 units.
For instance, if the base currency for your trading account is USD, your leverage is 1:400 and you are trading 1 lot EURUSD, the margin will be calculated like this:
(1 * 100 000/400) = 250 Euros
Euro is the primary currency of the symbol EURUSD, and because your account is USD, the system automatically converts the 250 EUROS to USD at the actual rate.