Okayama's 2025 population is now estimated at 718,616. In 1950, the population of Okayama was 123,666. Okayama experienced a decrease of -1,727 residents over the past year, marking an annual decline of -0.24%.These population estimates and projections come from the latest revision of the UN World Urbanization Prospects. These estimates represent the Urban agglomeration of Okayama, which typically includes Okayama's population in addition to adjacent suburban areas.