Convert mi² to km² and back. Geographic area comparisons from cities to countries, visual scale, and complete conversion tables.
The square miles to square kilometers converter provides precise bidirectional conversion between the two standard large-area units: mi² (used in the US and UK) and km² (used internationally). One square mile equals approximately 2.59 square kilometers.
Geographic area data appears constantly in news, education, and planning — but different sources use different units. American atlases report state areas in square miles, while the rest of the world uses square kilometers. This tool instantly translates between them and also provides acres, hectares, m², and ft² equivalents.
The built-in geographic reference table compares your measurement to real places from Vatican City (0.44 km²) to Russia (17.1 million km²), helping make abstract large numbers tangible. It is useful when preparing presentations, reports, or classroom materials that cite mixed unit systems. It also supports faster fact-checking when cross-referencing US and international datasets. That consistency is valuable when numbers are reused across maps, dashboards, and policy briefs.
Geographic area comparisons require consistent units. This tool converts mi²↔km² instantly and contextualizes the numbers by comparing to real cities, states, and countries — making large-area data meaningful and comparable across different sources. It reduces interpretation mistakes in planning, journalism, and policy analysis, especially when audiences span multiple unit conventions and reporting standards.
Square Miles to Square Kilometers: km² = mi² × 2.58999. Square Kilometers to Square Miles: mi² = km² ÷ 2.58999. Additional: 1 mi² = 640 acres = 2,589,988 m²; 1 km² = 100 hectares = 1,000,000 m².
Result: 258.999 km²
100 square miles × 2.58999 = approximately 259 km². This is about the size of a medium city — larger than Washington D.C. (177 km²) but much smaller than Chicago (607 km²).
The Public Land Survey System (PLSS) established the square mile as the fundamental US land unit. A township is 6×6 miles (36 mi²). Each township contains 36 sections of 1 mi² (640 acres). This system covers 30 states and forms the basis for property descriptions across the American West.
Area comparisons are powerful for understanding geography. Texas (695,662 km²) is larger than France (640,679 km²). Alaska (1.72M km²) is larger than India's Rajasthan, Madhya Pradesh, and Maharashtra combined. These comparisons only work when both measurements use the same unit.
Population density varies enormously: rural Alaska averages 0.5 people/mi² (0.2/km²), suburban America averages 2,000/mi² (770/km²), and Manhattan exceeds 70,000/mi² (27,000/km²). Understanding both area and density requires comfortable conversion between mi² and km².
Multiply by 2.58999. Example: 50 mi² × 2.58999 = 129.5 km². The factor comes from squaring the linear mile-to-km conversion: (1.60934)² = 2.58999.
One square mile = 2.59 km² = 640 acres = 27.9 million ft². Visually, it is a 1-mile × 1-mile area (1.6 km × 1.6 km) — roughly 18 city blocks × 18 city blocks in a typical grid.
The US is approximately 9,833,520 km² (3,796,742 mi² including water). This makes it the 3rd or 4th largest country by area, depending on how Chinas disputed territories are counted.
1 km² = 100 hectares. A hectare (ha) is 10,000 m² (100m × 100m). Hectares are used for farms and parks; km² for cities and countries.
The US customary system uses miles for long distances, so square miles is the natural large-area unit. The PLSS land survey system, established in 1785, divided land into 1-mile² sections, making mi² deeply embedded in US property records and law.
Divide population by area in km². Example: Manhattan has ~1.6M people in 59.1 km² = ~27,000 people/km² (≈70,000/mi²). This is one of the highest population densities in the world.