The square kilometer (km²) equals one million square meters and is used to measure large land areas such as cities, national parks, and countries. Geographic data, urban planning reports, and ecological studies rely on square kilometers as their standard area unit. One square kilometer equals approximately 0.3861 square miles or about 247.1 acres.

The square mile (mi²) is a large imperial area unit equal to 640 acres or about 2.59 square kilometers, used for measuring expansive territories like cities, counties, and national parks. Geographic data in the United States and United Kingdom frequently references square miles when describing regions, especially in population density calculations. One square mile equals exactly 2.58999 square kilometers.