This depends on a number of factors including the type of visa used to enter US as well as length of your past period of unlawful stay. Generally, if an alien accrues unlawful presence of 180 continuous days or more [but less than 1 year] and after which the alien leaves United States, the alien will be barred fro 3 years. An alien who accrues 1 year or more of unlawful presence and then departs the US, the alien is barred for 10 years. Unlike most other visas, calculation of unlawful presence period of F-1 and G-1 entrants is calculated differently. Unlike other visas, F-1 and G-1 visa entrants are admitted for duration of status. D/S and their I-94 does not indicate a definite calendar date after which they must leave the US or else start accruing unlawful status. For them, unlawful presence only begins to count from the date CIS makes a determination. To be sure, you should consult with an immigration attorney before you enter US , because, like any other visa, an F-1 visa is only an application for admission and you will be allowed to the US only after a CBP officer at the airport grants your application to enter.
Answered on Feb 26th, 2013 at 3:59 PM