Iwaki's 2026 population is now estimated at 353,321. In 1950, the population of Iwaki was 103,607. Iwaki experienced a decrease of -951 residents over the past year, marking an annual decline of -0.27%. 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 | 2026 Pop. ↓ | Growth |
|---|---|---|
| Tokyo | 36,953,600 | -0.22% |
| Osaka | 18,873,900 | -0.25% |
| Nagoya | 9,511,730 | -0.24% |
| Fukuoka | 5,453,200 | -0.23% |
| Yokohama | 3,777,491 | 1% |
| Shizuoka | 2,921,450 | -0.3% |
| Sapporo | 2,645,940 | -0.29% |
| Sendai | 2,330,920 | -0.29% |
| Hiroshima | 2,053,290 | -0.24% |
| Niigata | 791,952 | -0.26% |
| Kumamoto | 733,444 | -0.23% |
| Okayama | 716,815 | -0.25% |
| Kagoshima | 576,499 | -0.41% |
| Utsunomiya | 516,249 | -0.26% |
| Matsuyama | 500,662 | -0.3% |
| Oita | 473,310 | -0.23% |
| Kurashiki | 469,199 | -0.24% |
| Kanazawa | 460,005 | -0.25% |
| Fukuyama | 459,330 | -0.24% |
| Takamatsu | 413,604 | -0.24% |
| Toyama | 404,360 | -0.37% |
| Miyazaki | 393,787 | -0.24% |
| Nagasaki | 393,167 | -0.86% |
| Toyohashi | 364,054 | -0.31% |
| Takasaki | 363,347 | -0.23% |
| Nagano | 362,689 | -0.42% |
| Koriyama | 322,624 | -0.4% |
| Maebashi | 321,546 | -0.46% |
| Kochi | 318,399 | -0.58% |
| Asahikawa | 318,216 | -0.65% |
| Naha | 316,833 | -0.27% |
| Kurume | 300,782 | -0.25% |
| Akita | 294,304 | -0.7% |
| Okinawa | 142,840 | 1.01% |
