Will somebody please answer this for me?: I want to start day trading s&p e mini futures on Think or Swim. How does the margin work. I know as a PDT I get 4:1 for stocks, is it the same for futures? Or is it totally different. Say, I have 40 K in my account how many contracts can I purchase without using margin if I am using the entire bank at one time and how many contracts can I purchase using intraday margins. Much obliged.