Square Miles to Square Kilometers Converter: US Geographic Area in Metric Km2, Reverse Km2 to Sq Miles, Shows Acres, Hectares, and Square Meters
Convert any square miles value to square kilometers using the exact SI constant: 1 square mile = 2.589988110336 km2 (derived from 1 mile = 1609.344 m exactly). Results also show square meters, acres, and hectares. Reverse tab converts km2 back to square miles. Chart benchmarks your area against 6 US geographic references from Manhattan to Texas. Key facts: Texas = 268,596 sq miles = 695,660 km2. Rhode Island = 1,212 sq miles = 3,139 km2. Alaska = 663,268 sq miles = 1,717,856 km2. 1 sq mile = 640 acres = 258.999 ha. Free PDF report and WhatsApp share.
Square Miles to Square Kilometers Converter Tool
Enter square miles to convert to square kilometers
US examples: 1 sq mi (1 section). 22.83 (Manhattan). 1,212 (Rhode Island). 7,354 (New Jersey). 48,430 (Georgia). 163,696 (California). 268,596 (Texas). 663,268 (Alaska).
Your Area vs 6 US Geographic Benchmarks
Why the US Needs Both Square Miles and Square Kilometers
The United States measures geographic area exclusively in square miles for domestic purposes. The US Census Bureau publishes state, county, city, and census tract land areas in square miles. The National Weather Service issues watch, warning, and advisory areas in square miles. The Department of Interior manages national parks, wildlife refuges, and wilderness areas in acres and square miles. But the rest of the world uses square kilometers. Every international geographic database, from the United Nations to the World Bank to the OECD, publishes area data in square kilometers. When American scientists, journalists, government analysts, weather forecasters, and business professionals need to compare US data with global counterparts, the conversion becomes essential.
The conversion constant 2.589988110336 km2 per square mile is exact, not an approximation. It derives directly from the 1959 international definition of the foot (1 ft = 0.3048 m exactly), making 1 mile = 5,280 ft x 0.3048 m/ft = 1,609.344 m exactly, and therefore 1 square mile = 1,609.344 squared = 2,589,988.110336 m2 = 2.589988110336 km2 exactly. The commonly used approximation of 2.59 is close but introduces a 0.0038% error, which for large areas like Texas (268,596 sq miles) produces a discrepancy of approximately 10 km2.
How This Square Miles to Square Kilometers Converter Works
The Sq Miles to Sq Km tab multiplies your entered square miles by 2.589988110336 using Big.js arbitrary-precision arithmetic. The result shows square kilometers to 4 decimal places, plus square meters (multiply by 2,589,988.110336 exactly), acres (multiply by 640 exactly, the statutory acres-per-section definition), hectares (multiply by 258.9988110336 exactly), and square feet (multiply by 27,878,400 exactly). All these ancillary units flow directly from the primary conversion with zero rounding until the final display step.
The Sq Km to Sq Miles reverse tab divides your km2 input by 2.589988110336 using Big.js division, producing square miles to 4 decimal places plus square meters, hectares (km2 x 100 exactly), and acres. The comparison chart uses a logarithmic scale to display your entered area against 6 US reference benchmarks: 1 sq mile (one section), Manhattan Island (22.83 sq miles), Rhode Island (1,212 sq miles, the smallest state), New Jersey (7,354 sq miles), Georgia (48,430 sq miles), and Texas (268,596 sq miles, the largest contiguous US state). The logarithmic scale is essential here because these benchmarks span five orders of magnitude.
US State Areas: Every State in Square Miles and Square Kilometers
| State | Sq Miles | Sq Km | Acres | Rank |
|---|---|---|---|---|
| Alaska | 663,268 | 1,717,856 | 424,491,520 | 1st largest |
| Texas | 268,596 | 695,660 | 171,901,440 | 2nd largest |
| California | 163,696 | 423,971 | 104,765,440 | 3rd largest |
| Montana | 147,040 | 380,832 | 94,105,600 | 4th largest |
| New Mexico | 121,590 | 314,917 | 77,817,600 | 5th largest |
| Arizona | 113,990 | 295,234 | 72,953,600 | 6th largest |
| Nevada | 110,572 | 286,380 | 70,766,080 | 7th largest |
| Colorado | 104,094 | 269,601 | 66,620,160 | 8th largest |
| Wyoming | 97,813 | 253,335 | 62,600,320 | 9th largest |
| Florida | 65,758 | 170,312 | 42,085,120 | 22nd largest |
| Georgia | 59,425 | 153,911 | 38,032,000 | 24th largest |
| New York | 54,555 | 141,300 | 34,915,200 | 27th largest |
| Connecticut | 5,543 | 14,357 | 3,547,520 | 48th largest |
| Delaware | 2,489 | 6,446 | 1,592,960 | 49th largest |
| Rhode Island | 1,545 | 4,002 | 988,800 | 50th smallest |
Three Real US Scenarios: Square Miles to Square Kilometers in Practice
Dallas Fort Worth NWS Meteorologist Converting a Severe Thunderstorm Warning Polygon for WMO International Reporting
A National Weather Service meteorologist at the Dallas Fort Worth Weather Forecast Office issues a severe thunderstorm warning covering a polygon that encompasses portions of Tarrant, Dallas, and Collin counties. The warning text states the affected area is approximately 450 square miles. For automatic data feeds to international aviation weather services and the World Meteorological Organization’s aviation weather information systems, the area must be expressed in square kilometers. Converting: 450 sq miles x 2.589988110336 = 1,165.5 km2. The WMO’s international weather format (BUFR, GRIB2) uses km2 for hazard areas, while the NWS domestic warning text uses square miles. The NWS issues approximately 10,000 severe thunderstorm warnings per year; many require sq mile to km2 conversion for international data exchange. The NWS also publishes annual storm data in both square miles (for domestic NCEI archives) and square kilometers (for international WMO statistical submissions). The Dallas WFO’s county warning area covers approximately 25,000 square miles (64,749 km2), and the area affected by any given warning polygon is typically 100 to 2,000 square miles (259 to 5,180 km2).
Chicago Urban Planner Comparing City Density with Tokyo and London for an International Livability Study
An urban planner for the City of Chicago is preparing a comparative livability and density analysis for the city council, benchmarking Chicago against Tokyo and London. Chicago proper covers 227.3 square miles = 588.6 km2. The 2020 Census population of Chicago was 2,696,555. Chicago’s population density: 2,696,555 / 227.3 sq miles = 11,871 people/sq mile. Converting to the metric standard for international comparison: 11,871 people/sq mile x (1 sq mile / 2.58999 km2) = 4,583 people/km2. Tokyo (special wards area): 621.98 km2 (240.1 sq miles), population 9.7 million = 15,596 people/km2 (40,378 people/sq mile). London (Greater London): 1,572 km2 (606.9 sq miles), population 8.9 million = 5,659 people/km2 (14,655 people/sq mile). On the metric scale: Chicago at 4,583 people/km2 is less dense than London (5,659/km2) and far less dense than Tokyo (15,596/km2). On the US customary scale: Chicago at 11,871 people/sq mile is denser than the national average of 93.8 people/sq mile but comparable to other major US cities. Without the sq miles to km2 conversion, comparing Chicago to European and Asian cities in their native metric reporting format would be impossible.
US Census Bureau GIS Analyst Converting Maricopa County Arizona Area for an OECD Regional Statistics Submission
A GIS analyst at the US Census Bureau is preparing a regional statistics submission for the OECD’s Metropolitan Areas database, which requires area in square kilometers. Maricopa County, Arizona (home to Phoenix) is one of the most populous counties in the US. The Census Bureau’s official land area for Maricopa County is 9,224 square miles. Converting for the OECD submission: 9,224 sq miles x 2.589988110336 = 23,890.3 km2. The OECD defines “functional urban areas” and “metropolitan areas” using km2-based density thresholds: areas with more than 1,500 people/km2 (3,885 people/sq mile) are classified as “urban centers.” Greater Phoenix metro area had a 2020 population of 4.9 million over roughly 14,599 square miles (37,812 km2) of metropolitan statistical area, giving a density of about 335 people/sq mile (130 people/km2), which the OECD would classify as a “polycentric metropolitan area” rather than a single dense core. The Census Bureau publishes county and state areas in both sq miles (in its decennial census products) and km2 (in its international statistical submissions). All land area calculations for Census purposes are based on the 1983 North American Datum (NAD83) coordinate system, which uses metric units internally.
Four Expert Tips for Square Miles and Square Kilometers in US Contexts
The Exact Constant Is 2.589988110336, Not 2.59: When the Difference Matters
The commonly rounded approximation 2.59 km2 per square mile introduces a systematic error of 0.000012/2.590 = 0.00046%, or about 1.2 square meters per square mile. For a single section (1 sq mile), the error is trivial. For Texas (268,596 sq miles), using 2.59 instead of 2.589988110336 gives 695,863 km2 vs the exact 695,660 km2, a 203 km2 discrepancy. That 203 km2 is larger than the island of Nantucket. For international submissions to the United Nations Statistical Division, OECD, and World Bank, which archive historical country and subnational area data that researchers cite for decades, using the exact constant ensures your data matches the canonical international figures. The US Census Bureau and USGS use the exact constant in their official geographic area calculations.
Population Density: Converting People Per Sq Mile to People Per Sq Km
Population density conversion is the most common practical application of the sq miles to km2 relationship in the US. The US Census Bureau reports population density in people per square mile for all geographic units. International databases (Eurostat, OECD, UN Population Division) use people per square kilometer. To convert: people/sq mile / 2.589988110336 = people/km2. To go the other direction: people/km2 x 2.589988110336 = people/sq mile. US national average density: 93.8 people/sq mile = 36.2 people/km2. New York City: 26,403 people/sq mile = 10,194 people/km2. Los Angeles: 7,000 people/sq mile = 2,703 people/km2. Houston: 3,662 people/sq mile = 1,414 people/km2. The conversion factor is exactly the same as for area: you divide by 2.5900 (approx) to convert the density, because density = people/area and both numerator and denominator stay the same while only the area unit changes.
Is a Square Mile Bigger Than a Square Kilometer? The Four-Unit Area Hierarchy
Understanding the relative sizes of the four common area units helps contextualize any conversion. From smallest to largest: 1 km2 = 0.3861 sq miles. 1 sq mile = 2.5900 km2. So a square mile is larger than a square kilometer by a factor of 2.59. Put another way: you need about 2.59 square kilometers to equal 1 square mile. In the full hierarchy: 1 sq mile = 640 acres = 258.999 ha = 2.590 km2 = 2,589,988 m2. 1 km2 = 100 ha = 247.105 acres = 0.3861 sq miles = 1,000,000 m2. 1 ha = 10,000 m2 = 2.4711 acres = 0.003861 sq miles = 0.01 km2. 1 acre = 0.4047 ha = 0.001563 sq miles = 0.004047 km2. Memorizing that 1 sq mile is about 2.59 km2 (or just “about 2 and a half km2”) is sufficient for most conversational purposes, while the exact 2.589988110336 constant is needed for formal reporting to international bodies, government databases, and peer-reviewed publications where data precision and replicability are essential.
Why the US Uses Square Miles and the Rest of the World Uses Square Kilometers
The US system of square miles traces back to the British Imperial system of measurement, which the American colonies inherited and the United States retained after independence. The US Public Land Survey System (USPLS), established by the Land Ordinance of 1785, built the entire township-and-range system around the mile: a township is 6 miles x 6 miles = 36 square miles containing 36 one-square-mile sections. This system covers most of the US outside the original thirteen colonies and Hawaii, making the square mile the foundational unit of US land tenure, property law, and agricultural geography. The metric system, mandated for international use by the 1875 Metre Convention, uses the kilometer (1,000 meters) as its standard distance unit. The square kilometer (1 km2 = 1,000,000 m2) follows naturally. Congress has passed legislation encouraging but never fully requiring metrication of US measurement systems, so the US uniquely uses both systems in different contexts: miles and sq miles for domestic geography and property, but km and km2 in scientific, military, and international contexts.
Square Miles vs Square Kilometers in US Government Reporting and International Databases
USGS Topographic Quadrangles and International Mapping
The US Geological Survey publishes its standard 7.5-minute topographic quadrangle maps covering approximately 50 to 75 square miles (130 to 194 km2) depending on latitude. Each quad represents a precisely defined geographic area rooted in degree-minute-second coordinates rather than metric boundaries, making sq miles to km2 conversion important for any scientist who needs to describe the coverage area in both US customary and metric terms. For example, a study area described as spanning three adjoining quads at 40 degrees north covers roughly 192 square miles (497 km2), a figure that international reviewers need in km2 to understand scale. At 40 degrees north, a quad covers about 64 square miles (165.8 km2). USGS domestic maps label elevations in feet and distances in miles, but the Universal Transverse Mercator (UTM) coordinate overlay uses meters. International topographic mapping at equivalent scales uses kilometers throughout. When US geologists or environmental scientists reference a USGS quad in an international publication, converting sq miles to km2 allows readers using metric survey systems to understand the mapped area scope. The USGS National Map at nationalmap.gov provides area statistics in both square miles and square kilometers for scientific users working across measurement systems.
US Census Bureau: Dual Reporting of Geographic Area
The US Census Bureau publishes geographic area statistics in both square miles and square kilometers in different products. The decennial Census and American Community Survey data tables available at data.census.gov show land area and water area in square miles for states, counties, places, census tracts, and block groups. However, the Census Bureau’s TIGER/Line Shapefiles, which GIS professionals download for geographic analysis, include area attributes in square meters (metric) as the primary internal measurement unit, with square miles as a secondary derived field. The ALAND and AWATER fields in TIGER/Line shapefiles store area in square meters, which must be divided by 1,000,000 to convert to km2, or divided by 2,589,988.110336 to convert to square miles.
International statistical submissions from the Census Bureau to the UN Statistics Division, OECD, and World Bank use square kilometers throughout. The UN’s Demographic Yearbook, which publishes population and area data for all UN member states and territories, records US total area as 9,833,517 km2 (3,796,742 sq miles including inland water, per the CIA World Factbook). Researchers citing US area in international publications must convert the Census Bureau’s square mile figures to km2 for consistency with how other countries are reported. The exact conversion ensures that the published US figures match those in the international databases rather than creating small discrepancies that confuse citation chains.
National Weather Service Area Descriptions: Square Miles in Warnings and Km2 in Aviation
The National Weather Service issues weather warnings, watches, and advisories using geographic polygons defined by latitude/longitude coordinates. The area covered by a tornado warning, severe thunderstorm warning, or flash flood warning is routinely described in the warning text in square miles for domestic media and public consumption. NWS storm data, published by NOAA’s National Centers for Environmental Information (NCEI), archives maximum hail size, wind speed, and estimated damage path area (in square miles) for every documented significant weather event. Aviation weather products use different conventions. SIGMETs (Significant Meteorological Information) issued for the contiguous US domestic domestic market describe affected areas using CONUS references, while international SIGMETs issued through the ICAO (International Civil Aviation Organization) system use nautical miles and kilometers for area descriptions, consistent with ICAO standards. The NWS also produces gridded weather model output at grid spacings measured in km (the NAM model runs on a 12 km grid; the HRRR on a 3 km grid), even though forecast discussion products use miles and degrees Fahrenheit for domestic communication.
Quick Reference: Square Miles to Square Kilometers for US Geographic Areas
| Sq Miles | Sq Km | Acres | US Reference |
|---|---|---|---|
| 1 sq mi | 2.5900 km2 | 640 ac | 1 section (USPLS), 1 sq mile base unit |
| 36 sq mi | 93.240 km2 | 23,040 ac | 1 township (6×6 mile grid) |
| 100 sq mi | 258.999 km2 | 64,000 ac | County or large city footprint |
| 227 sq mi | 587.927 km2 | 145,280 ac | City of Chicago land area |
| 302 sq mi | 782.380 km2 | 193,280 ac | City of New York (all 5 boroughs) |
| 1,212 sq mi | 3,139.065 km2 | 775,680 ac | Rhode Island (smallest US state) |
| 9,224 sq mi | 23,890.3 km2 | 5,903,360 ac | Maricopa County, AZ |
| 9,349 sq mi | 24,213.8 km2 | 5,983,360 ac | Vermont |
| 48,430 sq mi | 125,385 km2 | 30,995,200 ac | Georgia |
| 163,696 sq mi | 423,971 km2 | 104,765,440 ac | California (3rd largest state) |
| 268,596 sq mi | 695,660 km2 | 171,901,440 ac | Texas (largest contiguous state) |
| 663,268 sq mi | 1,717,856 km2 | 424,491,520 ac | Alaska (largest US state overall) |
Frequently Asked Questions About Square Miles to Square Kilometers
Multiply square miles by 2.589988110336. That is the exact conversion constant derived from 1 mile = 1609.344 m. For rough estimates: multiply by 2.59. Examples: 1 sq mi x 2.5900 = 2.5900 km2. 100 sq mi x 2.5900 = 258.999 km2. 268,596 sq mi (Texas) x 2.5900 = 695,660 km2. The mental math shortcut is: multiply sq miles by 2.6 for a quick rough estimate, then subtract about 0.4% for better accuracy. The exact constant 2.589988110336 has 13 significant figures and produces zero rounding error for formal reporting.
1 square mile = 2.589988110336 km2 exactly. Rounded to common precision: 2.5900 km2 (4 decimal places), 2.590 km2 (3 decimal places), 2.59 km2 (2 decimal places). One square mile also equals 640 acres, 258.9988 hectares, 2,589,988.110336 square meters, and 27,878,400 square feet. The square mile is the fundamental unit of the US Public Land Survey System: one “section” is exactly 1 square mile (1 mile x 1 mile), and 36 sections make up one township. In metric terms, 1 sq mile is slightly less than 3 square kilometers (2.59 of them), which helps visualize its size relative to the metric unit.
1 square kilometer = 0.38610215855 square miles (rounded to 11 decimal places). Common approximations: 0.3861 sq mi (4dp), 0.386 sq mi (3dp). One square kilometer also equals 100 hectares, 247.1054 acres, 1,000,000 square meters, and 10,763,910 square feet. A square kilometer is a 1,000 m x 1,000 m square (about 3,281 feet x 3,281 feet), which is just under 1 mile x 1 mile (5,280 feet x 5,280 feet). One square kilometer is about 38.6% the size of one square mile. To remember: “one km2 is about a third of a square mile” is a useful rough approximation (actually 38.6%, so closer to 40%).
Yes, significantly. 1 square mile = 2.5900 km2, so a square mile is about 2.59 times larger than a square kilometer. This makes sense from the underlying dimensions: 1 mile = 1.60934 km, so 1 sq mile = 1.60934 squared = 2.590 km2. A square kilometer is a 1 km x 1 km square. A square mile is a 1 mile x 1 mile square. Since a mile is 1.609 km, the square mile is 1.609 x 1.609 = 2.590 times larger in area. The relationship between sq miles and km2 is the same as the square of the relationship between miles and km: (1.609344)^2 = 2.589988110336.
100 square miles = 258.9988 km2 = 64,000 acres = 258,998.8 hectares = 258,998,811 m2. Note that 100 sq miles = 258.999 km2 (approximately 259 km2). This is also approximately 1/640 of the area of one million acres: 640 sections x 1 sq mile/section = 640 sq miles of contiguous land in a 10×6-section rectangular block. A 100-sq-mile footprint is larger than many US cities: Dallas proper is about 340 sq miles (880 km2), Houston is about 669 sq miles (1,733 km2), but many mid-size cities occupy 50 to 200 sq miles. The area of Crater Lake National Park is approximately 286 sq miles (741 km2) including the lake.
Texas covers 268,596 square miles = 695,660 km2. This makes Texas the 2nd largest US state (after Alaska) and slightly smaller than France (551,695 km2) but significantly larger than any other European country. Texas is about 1.26 times the size of France, 2.69 times the size of Germany (357,114 km2), and about 7.1 times the size of the United Kingdom (242,495 km2). Texas has a north-south distance of about 801 miles (1,289 km) and an east-west distance of about 773 miles (1,244 km). In acres: 268,596 x 640 = 171,901,440 acres. Texas has approximately 127 million acres of agricultural land per USDA figures, the most of any US state.
The total US area (50 states plus DC) is 3,796,742 square miles = 9,833,517 km2 (total area including inland water bodies). US land area only (excluding water): approximately 3,531,905 sq miles = 9,147,593 km2. These figures make the United States the 3rd or 4th largest country in the world by area depending on source (some sources rank China above the US, others below, depending on disputed territories). By total area (9.83 million km2), the US is slightly larger than China (9.60 million km2) and slightly smaller than Canada (10.0 million km2) and Russia (17.1 million km2). The CIA World Factbook and UN Statistics Division both use km2 as their standard area unit, reporting the US at 9,833,517 km2.
10 square miles = 25.8999 km2 = 6,400 acres = 2,589.988 hectares. Ten square miles is the order of magnitude of a small US city or a large suburban municipality. The city of Manhattan (New York County) covers 22.83 square miles (59.1 km2), putting it in the same order of magnitude as 10 sq miles. Many smaller US cities and towns cover 5 to 15 square miles. A 10-sq-mile square would be a roughly 3.16 mile x 3.16 mile (5.09 km x 5.09 km) area, which is a meaningful geographic footprint for emergency planning, utility service territories, and school district boundaries.
50 square miles = 129.4994 km2 = 32,000 acres = 12,950 hectares. Fifty square miles is a meaningful footprint for regional geographic analysis. The entire island of Manhattan is 22.83 sq miles; a 50-sq-mile area would fit about 2.2 Manhattans. Many medium-sized US cities cover 30 to 70 sq miles: Austin, TX is approximately 322 sq miles (834 km2), but many smaller cities like Albuquerque (187 sq miles / 484 km2) or Kansas City, MO (319 sq miles / 827 km2) illustrate the range. A 50-sq-mile tornado damage swath (a rare but historically documented event) would be 129.5 km2, larger than the island of Manhattan.
Rhode Island, the smallest US state, has a land area of 1,212 square miles (the full area including water is 1,545 sq miles = 4,001 km2; land only is 1,212 sq miles = 3,139 km2). Converting land area: 1,212 sq miles x 2.589988110336 = 3,139.06 km2. Rhode Island is about 60 km from north to south and about 60 km from east to west at its widest. For comparison, Rhode Island’s 3,139 km2 is about 30% larger than Luxembourg (2,586 km2) but about half the size of Delaware (5,133 km2). In European terms, Rhode Island is comparable in size to a large French department or a small German state (Bundesland). The density of Rhode Island at 2020 population 1,097,379 over 1,212 sq miles = 905 people/sq mile = 349 people/km2, making it one of the densest US states despite its compact size.
500 square kilometers = 193.05 square miles = 123,553 acres = 50,000 hectares. Five hundred km2 is the scale of a small European nation or a large US metropolitan area. Singapore is 728 km2 (281 sq miles). Hong Kong is 1,108 km2 (428 sq miles). The five boroughs of New York City cover approximately 783 km2 (302 sq miles). Chicago proper is 589 km2 (227 sq miles). Los Angeles city is 1,299 km2 (501 sq miles). At 500 km2 (193 sq miles), a metropolitan area is considered mid-size to large by global urban standards, large enough to require significant transportation infrastructure but small enough that a car commute across the city is still feasible in under an hour.
1,000 square kilometers = 386.10 square miles = 247,105 acres = 100,000 hectares. A 1,000 km2 footprint is the scale of a mid-size European country or a large US county. Luxembourg has an area of 2,586 km2 (999 sq miles), making it almost exactly 1,000 km2 per “half-Luxembourg.” Tokyo’s Special Ward area (core 23 wards) covers 621 km2 (240 sq miles), while the greater Tokyo Metropolitan Government area covers 2,194 km2 (847 sq miles). At 1,000 km2, you have an area equivalent to about 4.3 Manhattans, or a square of land about 31.6 km (19.6 miles) on each side. Los Angeles County covers 10,520 km2 (4,061 sq miles), which is about 10.5 times larger than 1,000 km2.
The four area units relate to each other as follows. 1 square mile = 640 acres exactly (by US Public Land Survey System definition: 1 section = 1 sq mile = 36 x 160-acre quarter sections). 1 square mile = 258.9988 hectares (= 640 acres x 0.40469 ha/acre). 1 square mile = 2.5900 km2. Going the other direction: 1 km2 = 100 ha = 247.105 acres = 0.3861 sq miles. 1 ha = 2.4711 acres = 10,000 m2 = 0.01 km2. 1 acre = 0.4047 ha = 43,560 sq ft = 0.001563 sq miles. These exact relationships allow converting freely between any of the four units by first converting to acres (using the USPLS relationship) or to square meters (using SI definitions).
1 mile = 1.609344 kilometers exactly. This is not an approximation; it is the exact defined relationship since 1959 when the US, UK, Canada, Australia, New Zealand, and South Africa agreed on the international inch (25.4 mm exactly), making 1 foot = 0.3048 m exactly and 1 mile = 5,280 feet x 0.3048 m/ft = 1,609.344 m = 1.609344 km exactly. Squaring this gives 1 sq mile = (1.609344)^2 = 2.589988110336 km2 exactly. For practical conversions: 10 miles = 16.09 km. 26.2 miles (marathon) = 42.195 km. 60 mph = 96.56 km/h. 100 km/h = 62.137 mph. The mile-to-km relationship (1.609) is easy to remember as “about 1.6 km per mile” with the refinement that it is slightly more than 1.6.
Divide people per square mile by 2.589988 to get people per square kilometer. Or equivalently, multiply by 0.38610. Examples: US national average of 93.8 people/sq mile / 2.5900 = 36.2 people/km2. New York City 26,403 people/sq mile / 2.5900 = 10,194 people/km2. The division makes sense intuitively: since 1 sq mile = 2.59 km2, the same number of people spread over 1 sq mile are spread over 2.59 km2, so the density per km2 is lower by a factor of 2.59. The UN defines urban population as living in areas with more than 400 people/km2 (1,036 people/sq mile), and dense urban areas as having more than 1,500 people/km2 (3,885 people/sq mile). The US Census Bureau defines “urbanized areas” as having at least 1,000 people per square mile (386 people/km2), which translates directly using the sq mile to km2 conversion.
Alaska covers 663,268 square miles = 1,717,856 km2 of total area (including water). Land area only: approximately 571,951 sq miles = 1,481,347 km2. Alaska is the largest US state, covering about 17.5% of total US area. At 1.72 million km2, Alaska is larger than the combined area of France (551,695 km2), Germany (357,114 km2), Spain (505,990 km2), and Sweden (450,295 km2), totaling about 1.86 million km2 for those four major European nations combined. Alaska’s population density is about 1.3 people/sq mile (0.5 people/km2), the lowest of any US state by far, compared to the US national average of 93.8 people/sq mile (36.2 people/km2). If Alaska were a separate country, it would rank as the 18th largest nation by area.
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Legal Disclaimer and Editorial Transparency
This square miles to square kilometers converter uses the exact SI-derived constant: 1 sq mile = 2.589988110336 km2, calculated as (1609.344 m)^2 / 1,000,000 m^2/km^2, where 1609.344 m/mile is exact per the 1959 international definition of the foot. Results are computed using Big.js arbitrary-precision arithmetic and displayed to 4 decimal places. State area figures are from the US Census Bureau TIGER/Line geographic database and may differ slightly from other sources due to different reference dates or inclusion/exclusion of water bodies. Population density figures are based on 2020 decennial Census population counts divided by Census Bureau land area in square miles. Weather service area descriptions reference NWS and NOAA public documentation; always consult official NWS warnings directly for any weather emergency. Key authority references: NIST SP 811 (2008 edition, conversion factors) at nist.gov; US Census Bureau geographic data at census.gov; NOAA National Weather Service at nws.noaa.gov.