The formula for calculating margin in Forex trading is as follows;
"Number of lots x lot size x open price (USD) / 100 (leverage)"
Since the base currency for SvoFX trading account is USD, it is multiplied by the open price (USD) depending on the currency pair traded.
For example, if you want to trade 1.00 lot of GBPUSD = 1.30000;
1.00 x 100000 x 1.30000 / 100" = 1300USD.