The ISO symbol "km²" means "square kilometres" (not to be confused with "kilometres squared"). One of them contains 100 ha (hectares) and/or 1 million square metres (m²) and is a little over twice the size of Vatican City, just over half the size of Monaco (country ranked 192nd by area), and one-third of the size of the City of London.

The Imperial unit "square mile" contains approximately 2.5900 km².