data japan 2024The 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 NameAs of 2025, the population of Japan is projected at 123.10 million, compared to 123.75 million in 2025. It is the sixth-most populous country in Asia and ranks 12th in the e population