For FX currency pairs

Required Margin = Notional value * Trading Volume/ Leverage

Example: 1 lot EUR/USD at 1:500 Leverage: 100,000 EUR * 1/ 500 = 200 EUR

For Precious Metals

Required Margin = Volume * Contract Size * Open Price / Leverage

Example: 1 lot XAUUSD: 1 * 100 * 1,263.14 / 500 = $252.63

For Stocks/Equity CFDs

Required Margin = Volume * Contract Size * Open Price * Margin %

Example: 1 lot AAPL: 1 * 100 * 42.96 * 0.04 = $171.84

Calculation of Margin Level

Margin Level = Equity/Margin Used x 100

You can also calculate your margin level using their Margin Calculator.