Seahill is classified as a village by the NI Statistics and Research Agency (NISRA) (i.e. with population between 1,000 and 2,250 people). On Census day (29 April 2001) there were 1,186 people living in Seahill. Of these:
19.3% were aged under 16 years and 25.6% were aged 60 and over
50.3% of the population were male and 49.8% were female
15.3% were from a Catholic background and 75.6% were from a Protestant background