The following statistics on the population of Limerick come from the national census returns. These numbers can include a number of errors as the early returns were filled in by the local constabulary as a large portion of the general population was illiterate. There could be variants in the numbers as individuals could be omitted or counted twice if they were staying somewhere other than their normal place of residence on the night of the census returns.
The census was carried out every ten years from 1821 until 1911.
Population Changes 1821-1911
Population changes of the entire Limerick City and County:
| Year | Males | Female | Total | Percentage change |
| 1821 | 136,916 | 140,561 | 277,477 | ——— |
| 1831 | 153,625 | 161,730 | 315,355 | + 13.65 |
| 1841 | 161,997 | 168,032 | 330,029 | + 4.65 |
| 1851 | 127,387 | 134,745 | 262,132 | – 20.57 |
| 1861 | 105,712 | 111,565 | 217,277 | – 17.11 |
| 1871 | 93,112 | 98,824 | 191,936 | – 11.66 |
| 1881 | 88,311 | 92,321 | 180,632 | – 5.89 |
| 1891 | 78,607 | 80,305 | 158,912 | – 12.02 |
| 1901 | 72,456 | 73,642 | 146,098 | – 8.06 |
| 1911 | 72,229 | 70,840 | 143,069 | – 2.07 |
Due to the War of Independence and Irish Civil War, it was not possible to carry out a census of Ireland in 1921. The census was carried out every ten years from 1926 to 1946. It was then carried out every five years from 1946 onwards.
Limerick Population 1926-2006
Population of entire county, including city.
| Year | Population | Year | Population | Year | Population |
| 1926 | 140,343 | 1966 | 137,347 | 1991 | 161,956 |
| 1936 | 141,153 | 1971 | 140,459 | 1996 | 165,042 |
| 1946 | 142,559 | 1979 | 157,407 | 2002 | 175,304 |
| 1951 | 141,239 | 1981 | 161,661 | 2006 | 183,863 |
| 1961 | 133,339 | 1986 | 164,569 |
Native language distribution
Irish Speakers Limerick city and county 1851 and 1891:
| Limerick City | Limerick County | |||
| Year | Number of speakers | Percentage of local population | Number of speakers | Percentage of local population |
| 1851 | 76,982 | 37.4% | 4,204 | 7.9% |
| 1891 | 15,927 | 13.1% | 1,135 | 3.1% |
This number is those who self identified as Irish speakers. It is possible that bilingual individuals in other household were not recorded as Irish speakers as the head of the household completed the form.