What are built-up areas?
Built-up areas (BUAs) are a geography based on the physical built environment. They are created by using Ordnance Survey topographic information to identify distinct areas of developed land, such as cities, towns, and villages. This allows statistics to be published based on actual settlements rather than administrative boundaries.
BUAs are classified by population size as minor, small, medium, large or major, with the latest classifications based on Census 2021 populations, the latest available population estimates. There will be annual updates as part of the small area population estimates dataset.
The BUA geography was previously two tiered but the new version no longer includes larger areas such as Tyneside and Greater Manchester. Many of the larger 2021 BUAs are effectively successors to 2011 BUA subdivisions. However, populations for these areas at the two censuses cannot be directly compared because of boundary changes.