Its depends on what you free margin you put into. If you going to put 50% free margin then when your free margin fall into 50% then you will get MC. I don't recommend that you going to leave your account floating when you reach below 200% free margin. Right now on average my free margin is 500%. My plan is to have a free margin of 1000%. But 500% will do and I always make sure that once its reach below 300% I will try to make sure that my free margin will not going to reach 200%.