As of March 1, 2010, the city has an estimated population of 731,286 and a population density of 1,880 persons per km2. The total area is 389.53 km2.
Greater Kumamoto (熊本都市圏) had a population of 1,460,000, as of the 2000 census. It is not considered part of the Fukuoka–Kitakyushu metropolitan area, despite their shared border. The city was designated on April 1, 2012 by government ordinance.