Census data for Skælskør købstad
| 1787 | 24 | 501 | 239 | 47.70% | 262 | 52.30% | 0 | 0.00% | 0 |
| 1801 | 30 | 567 | 274 | 48.32% | 293 | 51.68% | 0 | 0.00% | 0 |
| 1834 | 40 | 850 | 405 | 47.65% | 445 | 52.35% | 0 | 0.00% | 0 |
| 1840 | 28 | 942 | 480 | 50.96% | 462 | 49.04% | 0 | 0.00% | 0 |
| 1845 | 32 | 965 | 514 | 53.26% | 451 | 46.74% | 0 | 0.00% | 0 |
| 1850 | 50 | 1,146 | 592 | 51.66% | 546 | 47.64% | 8 | 0.70% | 0 |
| 1855 | 2 | 22 | 8 | 36.36% | 14 | 63.64% | 0 | 0.00% | 22 |
| 1860 | 49 | 1,559 | 760 | 48.75% | 798 | 51.19% | 1 | 0.06% | 26 |
| 1870 | 319 | 1,704 | 835 | 49.00% | 867 | 50.88% | 2 | 0.12% | 1,704 |
| 1880 | 377 | 1,928 | 931 | 48.29% | 997 | 51.71% | 0 | 0.00% | 1,923 |
| 1890 | 647 | 437 | 190 | 43.48% | 247 | 56.52% | 0 | 0.00% | 437 |
| 1901 | 844 | 2,561 | 1,208 | 47.17% | 1,352 | 52.79% | 1 | 0.04% | 2,318 |
| 1906 | 861 | 2,544 | 1,196 | 47.01% | 1,348 | 52.99% | 0 | 0.00% | 0 |
| 1911 | 935 | 95 | 42 | 44.21% | 48 | 50.53% | 5 | 5.26% | |
| 1916 | 1,066 | 0 | 0 | 0.00% | 0 | 0.00% | 0 | 0.00% | |
| 1921 | 819 | 0 | 0 | 0.00% | 0 | 0.00% | 0 | 0.00% | |
| 1925 | 1,206 | 4 | 1 | 25.00% | 1 | 25.00% | 2 | 50.00% | |
| 1930 | 1,792 | 2,862 | 1,361 | 47.55% | 1,500 | 52.41% | 1 | 0.03% | 2,714 |
| 1940 | 1,937 | 0 | 0 | 0.00% | 0 | 0.00% | 0 | 0.00% | |