There is no minimum. In theory, you can immediately leave the United States and turn around and come back in.However, every time you make entry you have to convince the immigration officer that your purpose for entry is legitimate tourism, rather than an attempt to illegally reside in the United States. If you fail to convince the immigration officer this (and the burden of proof is always on you), your entry will be denied.It is thus incumbent on you to not give the impression that this is what youu2019re doing. There is no specific guidance as to how long you have to remain outside the United States before returning for a new visit. Obviously, the shorter that time, the more likely the immigration officer will be suspicious. This is especially true if you have a pattern of long visits broken only by short trips home.