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.

The mu (亩) is a traditional Chinese unit of area equal to approximately 666.67 square meters, used extensively in Chinese agriculture, rural land contracts, and property records. Farmland in China is almost always measured in mu, and government policies regarding grain production quotas reference this unit. One mu equals roughly 0.1647 acres or about 7,176 square feet.