Convert Acre (ac) to Square Mile (mi²) instantly.
About these units
Acre (ac)
An acre is a traditional Anglo-American land unit equal to 43,560 square feet, or roughly 4,047 m². It originated from medieval English farming, where an acre represented the amount of land a yoke of oxen could plow in one day—reflecting its deep agricultural roots. The acre remains widely used in the United States and the UK (in certain contexts), especially in real estate, agriculture, and land conservation. It is culturally intuitive for rural populations, where land plots have been measured in acres for centuries. The unit's longevity demonstrates how historical agricultural practices shaped modern land evaluation systems. Despite its lack of coherence with the metric system, the acre endures because of its cultural familiarity and long-standing legal integration.
Square Mile (mi²)
A square mile equals 640 acres or about 2.58999 km². It is the primary unit for describing large areas in the United States and the UK, particularly in geography and land-use planning. City sizes, county boundaries, national park dimensions, and lake surfaces are often expressed in square miles. Because of its large scale, it is ideal for measuring political subdivisions, conservation zones, and territorial claims. The square mile also appears in demographic statistics—such as population density—and in historical surveys of American frontiers, where square-mile sections formed the backbone of land distribution policies.