 It has an area of 634.89 km², making it the smallest regency in East Java.As at the 2010 Census, Sidoarjo Regency had a population of 2,191,489 ; the latest official estimate (as at 2014) is 2,279,034 .The regency is part of the urban region surrounding Surabaya, known as 'Gerbangkertosusila' area.