How long is K1 visa valid for?

The I-129F petition is valid for four months from the date of approval by USCIS. A consular officer can extend the validity of the petition if it expires before visa processing is completed. Also according to 90 day rule, applicant have 90 days from date of entry to get married. If a K-1 visa holder does not marry his or her U.S. citizen petitioner within 90 days of entry, then he or she must depart the United States within 30 days. Once you are married, you can apply to adjust status within US.