Countries of the United Kingdom by population
The population of the countries and regions of the United Kingdom was last measured by census in 2011. and the Census organisations have produced population estimates for subsequent years by updating the census results with estimates of births, deaths and migration in each year. The census results, and the annual population estimates, summarised below show that England is by far the most populous country of the United Kingdom and its population is therefore also presented by region.
 Population UK, Countries and Regions Feb 2017
|Rank||Name||Population (2015)||Percent of UK (2015)||Area||Pop.density (2011)||Population (2011)|
|4||Northern Ireland||1,851,621||2.8%||13,843 km²||130.81/km²||1,814,318|
|United Kingdom||65,110,034||100%||243,789 km²||259.16/km²||63,285,145|
- "Table 2 2011 Census: Usual resident population and population density, local authorities in the United Kingdom" (XLS). Office for National Statistics. 2012. Retrieved 19 December 2012.
- Population Estimates for the UK, England and Wales, Scotland and Northern Ireland, mid-2013, retrieved 3 May 2015