| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Boise City | 1 | 238,853 | 236,033 | 0.18% | 2,774 | 86 | City |
| Meridian | 2 | 148,009 | 119,506 | 3.51% | 3,935 | 38 | City |
| Eagle | 3 | 35,112 | 31,630 | 1.31% | 763 | 46 | City |
| Kuna | 4 | 32,665 | 24,526 | 3.62% | 1,252 | 26 | City |
| Star | 5 | 22,547 | 11,488 | 8.01% | 1,910 | 12 | City |
| Garden City | 6 | 13,203 | 12,292 | 1.2% | 3,235 | 4 | City |
Boise City is the largest city in Ada County, with a population of 238,853.
Garden City is the smallest city in Ada County, with a population of 13,203.
There are 6 cities in Ada County, Idaho.