data japan 2024Total current population for Japan in 2025 is 121,960,408, a 0.55% dec from 2025.. Total population for Japan in 2025 was 122,631,432, a 0.54% dec from 2025.; Total populationThe 2025 population density in Japan is 338 people per Km2 (875 people per mi2), calculated on a total land area of 364,555 Km2 (140,755 sq. miles). Largest Cities in Japan City Name