Learn how margin trading works, including understanding the risks and potential reward of trading on margin with our margin trading calculator. Forex accounts are held and maintained at GAIN Capital. Forex accounts are NOT PROTECTED by the SIPC. View all Forex disclosures. Forex, options and other leveraged products involve significant risk Forex Margin Calculator - Good Calculators Home » Forex Calculators » Forex Margin Calculator. Forex Margin Calculator. With the use of this free online Forex Margin Calculator, the user will be able to figure out exactly how much is required to have in his or her account to keep holding open positions.