How to calculate margin requirement (in MT4):

Position value* / leverage (e.g.100) = Margin required.
Remember to convert back to your account currency.

*Position value = contract size X lot size of trade.
Example (AUD account): 1.3 lots EURUSD with leverage 1:100.

Step 1: 1.3 lots X EUR100,000 = EUR130,000 position value.
Step 2: EUR130,000 / 100 (1:100 leverage) = EUR1300.
Step 3: EUR1300 X EURAUD = AUD$2137 Margin required.

Here's a helpful Margin Calculator:
https://www.afterprime.com/pip-calculator/