Different securities have different margin requirements. The standard initial margin requirement for equities and ETFs trading above $3/share is 50%. This means that half of the money needed for the purchase of these stocks can be borrowed. Stocks trading at less than $3/share, options, certain levered ETFs and certain volatile securities can be held at 100% margin requirement. This means that no funds can be borrowed when purchasing these securities. Occasionally, certain securities will be held at between 50% and 100% requirement. Subtract this requirement from 100% to figure out how much of the purchase can be borrowed funds.