Iwaki's 2025 population is now estimated at 354,272. In 1950, the population of Iwaki was 103,607. Iwaki experienced a decrease of -915 residents over the past year, marking an annual decline of -0.26%.These population estimates and projections come from the latest revision of the UN World Urbanization Prospects. These estimates represent the Urban agglomeration of Iwaki, which typically includes Iwaki's population in addition to adjacent suburban areas.
| City | 2025 Pop. ↓ | Growth |
|---|---|---|
| Tokyo | 37,036,200 | -0.21% |
| Osaka | 18,921,600 | -0.24% |
| Nagoya | 9,534,790 | -0.23% |
| Fukuoka | 5,465,920 | -0.22% |
| Shizuoka | 2,930,170 | -0.18% |
| Sapporo | 2,653,580 | -0.28% |
| Sendai | 2,337,590 | -0.16% |
| Hiroshima | 2,058,190 | -0.23% |
| Niigata | 793,974 | -0.24% |
| Kumamoto | 735,149 | -0.22% |
| Okayama | 718,616 | -0.24% |
| Kagoshima | 578,881 | -0.4% |
| Utsunomiya | 517,568 | -0.24% |
| Matsuyama | 502,185 | -0.29% |
| Oita | 474,415 | -0.22% |
| Kurashiki | 470,339 | -0.23% |
| Kanazawa | 461,142 | -0.24% |
| Fukuyama | 460,453 | -0.23% |
| Takamatsu | 414,621 | -0.23% |
| Toyama | 405,849 | -0.36% |
