5 years.

* has been legally admitted in the US for permanent residence;
* has lived continuously as a lawful permanent resident in the country for at least 5 years prior to filing with no single absence from the United States of more than one year;
* has been physically present in the US for at least 30 months out of the previous five years (absences of more than six months but less than one year shall disrupt the applicant's continuity of residence unless the applicant can establish that he/she did not abandon his/her residence during such period) ; and
* has stayed within a state or district for at least three months.