þéttbýli

Þéttbýli is the Icelandic statistical term for an urban area. It denotes a densely built-up area with at least 200 inhabitants, in which the distance between buildings does not exceed 200 meters. The definition is used by Statistics Iceland to distinguish populated urban settlements from rural areas and dispersed countryside.

The boundaries of a þéttbýli are determined from geospatial data on building locations and footprints. A contiguous cluster of buildings is classified as a single þéttbýli if there are no gaps between buildings larger than 200 meters. Areas that do not meet the 200-inhabitant threshold or where gaps between buildings exceed 200 meters are not counted as urban, even if they contain some development. Thus, an area can contain several þéttbýli within a single municipality, or none at all.

Þéttbýli serves as a statistical and planning category rather than an administrative unit. It is used in population statistics, infrastructure planning, service provision, and urban development analyses. Because boundaries are based on the built environment rather than political borders, changes in construction or demolition can alter which areas are classified as þéttbýli over time.

In practice, the concept helps describe how population and development are concentrated in Iceland, enabling comparisons across regions and over periods. It remains a standard measure in Icelandic statistics for identifying urban settlements and tracking urbanization.