In its almost 2.800 years of existence, the city had its ups and downs. The number of inhabitants in imperial times has been estimated between 1/1.5 million. Here is a list from Luciani (Roma Sotterranea):
| XIII BC | @ 5.000 |
| VIII - V | 80.000 |
| IV | 300.000 |
| II | 300.000 |
| I | 800.000 (400.000) |
| I AD | 1.000.000 (1.500.000) |
| II | 1.500.000 |
| V | 500.000 |
| end of V | 100.000 |
| VI | 100.000 |
| VII | 80.000 |
| IX | 35.000 |
| 1084 | 15.000 |
| 1377 | 17.000 |
| 1527 | 55.000 |
| 1550 | 60.000 |
| 1748 | 150.000 |
| 1800 | 153.000 |
| 1870 | 226.000 |
| 1895 | 450.000 |
| 1950 | 1.000.000 |
| 1980 | 3.000.000 |
| 2001 | *2.656.000 |
| *municipality of Rome |
