At the 2001 UK census, the City of Lancaster had a total population of 133,914. Of the 55,839 households in the city, 33.5% were married couples living together, 31.9% were one-person households, 7.8% were co-habiting couples and 10.0% were lone parents. These figures were similar to the national averages.
The population density was 233 /km2 (600 /sq mi) and for every 100 females, there were 91.8 males. Of those aged 16–74 in Lancaster, 26.7% had no academic qualifications, lower than 28.9% in all of England. The city of Lancaster had a higher proportion of white people than Lancashire and England.
The table below details the population change since 1801, including the percentage change since the last available census data. Although the City of Lancaster has existed as a district since 1974, figures have been generated by combining data from the towns, villages, and civil parishes that would later be constituent parts of the city.
At the 2001 UK census, 76.3% of Lancaster's population reported themselves as Christian, 0.6% Muslim, 0.3% Buddhist, 0.1% Hindu, 0.1% Jewish, and 0.1% Sikh. 13.6% had no religion, 0.3% had an alternative religion and 8.7% did not state their religion. The city is covered by the Roman Catholic Diocese of Lancaster, and the Church of England Diocese of Blackburn.
At the United Kingdom Census 2001, the City of Lancaster had 97,365 residents aged 16 to 74. Of these people, 4.0% were students with jobs, 9.6% students without jobs, 5.1% looking after home or family, 6.0% permanently sick or disabled and 2.8% economically inactive for other reasons.
In 2001, of the 55,906 residents of the City of Lancaster in employment, the industry of employment was 16.7% retail and wholesale, 14.2% health and social work, 11.4% education, 11.2% manufacturing, 7.8% property and business services, 6.7% construction, 6.7% hotels and restaurants, 6.5% transport and communications, 5.7% public administration and defence, 2.5% finance, 2.4% energy and water supply, 2.2% agriculture, 0.4% mining, and 5.3% other. This was roughly in line with national figures,although the proportion of jobs in agriculture which was more than the national average of 1.5% and the percentage of people working in finance and was below the national average of 4.8%; the proportion of people working in property was well below the national average of 13.2%.