Convert km² to mi² square kilometres ↔ square miles Free Online Secure
Type a value in square kilometres and read it in square miles at once. The factor is exact by definition, the arithmetic happens in your browser, and nothing is sent anywhere.
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Common values — Convert km² to mi² (square kilometres ↔ square miles)
| km² | mi² |
|---|---|
| 1 | 0.386102158542 |
| 2 | 0.772204317085 |
| 3 | 1.15830647563 |
| 5 | 1.93051079271 |
| 10 | 3.86102158542 |
| 20 | 7.72204317085 |
| 50 | 19.3051079271 |
| 100 | 38.6102158542 |
Where these units come from
Square units need no definition of their own: a square metre is a metre by a metre, and everything follows from the length. The land measures are older and stranger. The acre began as the land a yoke of oxen could plough in a day, which is why it was long and thin rather than square — one chain by one furlong, 4840 square yards. The hectare and the are came out of the French Revolution, when land had to be measured in something decimal; neither belongs to the International System, but both were kept for land because a hectare is a comfortable size to picture and a square metre is not. Since the 1959 agreement on the yard, the acre is exactly 4046.8564224 square metres, so the conversions on this page are exact rather than approximate.
Where you meet them
Square metres price flats, size carpets and decide how much paint a wall needs; square feet do the same work in the United States and in much of the property market worldwide. Hectares belong to farmland, forests and planning permissions; acres to land deeds in the English-speaking world. Square kilometres and square miles are for countries, lakes and fires. Square centimetres and square millimetres live in workshops, on datasheets and anywhere a cross-section matters.
Questions people ask
How big is a square kilometre?
A square one kilometre on each side, which is 100 hectares or 1,000,000 square metres. Central Park in New York covers about 3.4 square kilometres, and the whole of Monaco about 2. It is the natural unit for countries, lakes, forests and cities, where the figures in square metres would run to many digits.
How many acres are in a square mile?
640 acres, and a square mile is exactly 2.589988110336 square kilometres. American land surveys divided territory into sections of one square mile, which is why 640 acres is such a recognisable figure. For larger regions the square kilometre is more convenient.
Is the answer exact?
Where both units are defined in terms of one another by whole numbers, yes — the page says so above the figure, and the only rounding is in how many digits are shown. Where the ratio has no finite decimal, the page shows twelve significant digits and says the relation is approximate rather than pretending otherwise.
Does anything I type leave my device?
No. The arithmetic runs in your browser; nothing is uploaded and there is no server to upload it to. Load the page once and it keeps working with the network switched off.
From the metric atlas to the American almanac
Most of the world measures regions in square kilometres, but American and British sources use square miles, and the two numbers often meet in the same story: a flood of 290,000 km², a hurricane zone of 90,000 mi², a moon of 14.6 million square miles. To convert km² to mi² you multiply by 0.3861, about two fifths with a small correction. So 100 km² is 38.6 mi², and 1,000 km² is 386 mi². This page multiplies as you type, and the text below shows where the conversion matters, from radio coverage to the surface of Mars.
You will find the rule with worked examples, short profiles of both units, a comparison, a long tour of real situations and a list of the mistakes people make most often. The calculation runs in your browser and nothing you type is sent anywhere.
How to convert km² to mi²: multiply by 0.3861
The rule
One square kilometre equals 0.38610216 square miles. To convert km² to mi², multiply the square kilometres by 0.3861. So 10 km² is 3.86 mi², 50 km² is 19.3 mi², 250 km² is 96.5 mi² and 1,000 km² is 386.1 mi². To go back, one square mile is 2.58999 km², so multiply square miles by 2.59.
Worked examples
Hurricane damage over 233,000 km² is 90,000 mi². A county of 1,800 km² is 695 mi². A radio station with a coverage of 7,854 km² reaches 3,032 mi². For an estimate, multiply by 0.4 and subtract 4 per cent: 500 km² gives 200, minus 8, which is 192, against 193 exactly.
The square of 0.6214
A kilometre is 0.6214 miles, and an area is a length times a length, so the factor is 0.6214 squared, 0.3861. Using 0.6214 directly on an area makes the answer 61 per cent too large, one of the commonest slips with this conversion.
A quick check
The square mile is the larger unit, so the number must shrink to less than half. If your “convert km² to mi²” calculation gave you a bigger number than the one you started with, you divided instead of multiplying.
The square kilometre
One thousand metres on a side
The square kilometre is a million square metres, 100 hectares or 0.386 square miles. It is the unit of countries, regions and lakes in most of the world, and the base of population density in people per square kilometre.
Where it appears
Atlases, official statistics, textbooks and news in nearly every country outside the United States and the Anglophone press.
The square mile
One mile on a side
The square mile is 2.59 km², 259 hectares or 640 acres. It is used in the United States and the United Kingdom for countries, states, cities and parks, and for population density in people per square mile.
Where it appears
American statistics, British news, aviation charts and records of weather and disasters.
Square kilometre and square mile compared
A square mile is about 2.59 times as large as a square kilometre. A region of 100,000 km² has 38,610 mi². The figures describe different scales, so a reader who meets a number from the other system must know which one it is.
Because the factor is not round, mental conversion is an approximation. Multiply by 0.4 and take off 4 per cent for a quick estimate, and use 0.386102 for exact work.
Where the conversion appears
The surface of other worlds
The Moon has a surface of 37.9 million km², 14.6 million mi². Mars has 144.8 million km², 55.9 million mi², nearly exactly the same as the land area of the Earth, 149 million km², 57.5 million mi². Mercury has 74.8 million km², 28.9 million mi². Science articles use both units, and a “convert km² to mi²” calculation puts them side by side.
Radio and mobile coverage
An FM station with a radius of 50 km covers 7,854 km², 3,032 mi². A mobile tower with a 5 km radius covers 78.5 km², 30.3 mi². A rural cell network of 40 towers could therefore reach about 1,200 mi². Telecom regulators in America give coverage in square miles, and in Europe in square kilometres.
Disasters and relief
Hurricane Katrina affected about 90,000 mi², 233,000 km², of the US Gulf Coast. The 2022 floods in Pakistan covered one third of the country, about 290,000 km², 112,000 mi². Relief agencies describe the area in the unit of their donors, so both figures circulate.
Search and rescue
A search area of 100 km², 38.6 mi², is typical for a lost hiker. For an aircraft missing at sea, search zones reach 10,000 km², 3,861 mi², or more. Coast guards use square nautical miles, a third unit, 3.43 km², so conversions between three units are routine in search planning.
Time zones and territory
Russia spans 11 time zones, and its area of 17.1 million km², 6.6 million mi², is bigger than Pluto's surface. The United States, with 9.8 million km², 3.8 million mi², spans six time zones. Such comparisons turn up in encyclopaedias with areas in both units.
Fisheries and marine zones
A marine reserve of 12,000 km², 4,630 mi², may protect a reef. The Great Barrier Reef Marine Park has 344,400 km², 133,000 mi². Ocean zones are often given in square kilometres for science and square miles for American policy, so conversions are routine for those who follow marine protection.
Glaciers in the Alps and Rockies
The Aletsch Glacier covers about 80 km², 31 mi². Glacier National Park in Montana has 4,100 km², 1,583 mi², with fewer than 30 glaciers left. Alpine guides give the extent in square kilometres, American ones in square miles.
Space and astronomy
The cross section of the Earth is about 127 million km², 49 million mi². The Sun's surface is 6.09 trillion km², 2.35 trillion mi². These huge numbers are written in scientific notation, but the underlying factor is still 0.3861, and a “convert km² to mi²” calculation applies at every scale.
Rounding
The factor 0.386102 is accurate to six digits. For countries, keep three or four significant figures: 83,871 km² is 32,382 mi². If the source says about 84,000 km², write about 32,400 mi².
Spreadsheet use
Put square kilometres in column A and =A2*0.386102 in column B. For the reverse, use =B2*2.58999. Format with one decimal for large areas. A third column with =A2*100 gives hectares.
Teaching the idea
Draw a map grid where each square is one mile, then overlay a kilometre grid. A mile square is slightly bigger than two and a half kilometre squares. Students who count the squares see that 2.59 km² fit in a square mile, and understand why 0.386 is its inverse.
Population density
A density of 100 people per km² is 259 per mi². The United States has 36 per km², 93 per mi². Bangladesh has 1,300 per km², 3,400 per mi². To convert density, multiply the per km² number by 2.59, not by 0.386, which is the opposite of what is needed for areas.
Land held by companies and trusts
A timber company holding 12,000 km², 4,633 mi², is bigger than Delaware. A country estate of 100 km², 38.6 mi², would be a large property anywhere. Annual reports give land in acres or hectares, but newspapers convert to square miles for readers, so the figure passes through several units.
Harbours, bays and estuaries
San Francisco Bay covers about 1,240 km², 479 mi², and Chesapeake Bay 11,600 km², 4,479 mi². The Thames Estuary has roughly 300 km², 116 mi². Coastal managers give areas in the unit of their funders, and a “convert km² to mi²” calculation is needed when two bays are compared in a report with figures from both sides of the Atlantic.
Wildfires in California
The Dixie Fire of 2021 burned about 3,900 km², 1,505 mi². The August Complex of 2020 burned 4,090 km², 1,579 mi². American agencies report acres and square miles, while European and Australian ones report hectares and square kilometres, so a “convert km² to mi²” calculation is needed to compare events.
Cities from above
The urban area of Los Angeles is about 6,300 km², 2,432 mi², and that of Chicago about 5,500 km², 2,123 mi². London's built up area is 1,738 km², 671 mi², and Paris 2,845 km², 1,098 mi². Statistical agencies define cities differently, and city comparisons only make sense when the same definition and the same unit are used.
Islands for sale and private estates
Private islands range from 0.01 km², 1 hectare, to 150 km², 58 mi². Estate agents often use acres, so a hundred acre island is 0.4 km², 0.16 mi². When an island is described in both square kilometres and square miles in different parts of a brochure, a “convert km² to mi²” calculation helps to verify that they refer to the same size.
Telecommunication networks and satellites
A satellite beam may cover 200,000 km², 77,200 mi². A low orbit constellation covers the Earth in thousands of cells of about 500 km², 193 mi², each. Network engineers work in square kilometres in design documents, but marketing material for American customers states coverage in square miles.
Farmland lost to cities
Between 1992 and 2012, the United States lost about 31 million acres of farmland, 48,000 mi², 125,000 km², to development. Europe loses about 1,000 km², 386 mi², of farmland each year to sealing. The figures come from different agencies in different units, and a conversion is the first step to compare the two trends.
Reading old atlases
Atlases from the early twentieth century give areas in square miles for the British empire and in square kilometres for continental Europe. A researcher who compares two such atlases must convert every figure, and the factor 0.3861 appears again and again. It is a good habit to note the unit beside every number you copy.
A table of anchors
Learn a few pairs and you can check any result. 10 km² is 3.86 mi², 26 km² is about 10 mi², 100 km² is 38.6 mi², 259 km² is exactly 100 mi², and 1,000 km² is 386 mi². Between those anchors you can interpolate by eye. A quick look at the anchors tells you at once whether a figure that came out of a “convert km² to mi²” calculation is believable, and it protects against a slipped decimal point in a report that will be read by many people.
When the unit is not stated
Many news articles write "square miles" for an area but "miles" for a distance and then drop the word square. If an American article says that a fire grew to 250 miles, it probably means 250 square miles, which is 647 km². Before you convert, make sure that the number is an area. If the context is unclear, look for words such as acres, burned, covered or across, and for the original source.
Spreadsheets with mixed sources
If you collect areas from several sources in one table, add a column for the unit and fill it for every row. Then add a hidden column that converts everything to square kilometres. Only the hidden column feeds charts and totals, so a single row in miles cannot spoil the result. This habit costs a minute and saves a lot of cleaning later when somebody asks where a number came from.
Tornado outbreaks and storm tracks
A typical tornado track is 2 km wide and 25 km long, 50 km², 19 mi². A severe outbreak may affect 100,000 km², 38,610 mi². The Storm Prediction Center in the United States uses square miles for watch areas, while European weather services use square kilometres for warnings.
The Dust Bowl and soil erosion
The Dust Bowl of the 1930s hit about 400,000 km², 154,400 mi², of the American plains. Modern studies of soil erosion measure land in hectares or square kilometres, while historical accounts use square miles. A student of history must translate between them.
Light pollution and dark sky areas
A dark sky reserve of 690 km², 268 mi², such as Exmoor National Park in England, protects the night sky. The Pic du Midi in France covers 3,100 km², 1,200 mi². Conservation groups publish sizes in square kilometres, and American associations in square miles, so a conversion appears on international pages.
Rainfall zones and climate classes
Climatologists divide the world into zones by rainfall. A zone receiving 500 to 1,000 mm per year may cover 40 million km², 15.4 million mi². Climate atlases in different languages give areas in different units, which is why conversion is routine for those who write about climate.
Native lands and reservations
The Navajo Nation covers about 71,000 km², 27,400 mi², the largest reservation in the United States, bigger than West Virginia. Aboriginal land trusts in Australia cover millions of square kilometres. Legal documents give area in the unit of the country, and reporters convert them for international readers.
Arctic sea ice
The Arctic sea ice extent at its summer minimum is about 4 million km², 1.5 million mi². In winter, it peaks near 15 million km², 5.8 million mi². The US National Snow and Ice Data Center gives both units, and the conversion is part of every report.
Counties and districts
A typical English county covers 2,000 to 3,000 km², 770 to 1,160 mi². An American county has an average of 1,000 mi², 2,590 km². The largest, San Bernardino County, has 20,105 mi², 52,070 km². A “convert km² to mi²” calculation brings such numbers together when you compare administrative units.
More values for convert km² to mi²
A longer list of conversions
If the value you need is not in the first list, these further conversions may be close enough to read off directly:
- 0.1 km² = 0.0386102 mi²
- 0.5 km² = 0.193051 mi²
- 3 km² = 1.15831 mi²
- 4 km² = 1.54441 mi²
- 7 km² = 2.70272 mi²
- 15 km² = 5.79153 mi²
- 20 km² = 7.72204 mi²
- 75 km² = 28.9577 mi²
- 200 km² = 77.2204 mi²
- 500 km² = 193.051 mi²
- 2,000 km² = 772.204 mi²
- 10,000 km² = 3,861.02 mi²
Mistakes when you convert km² to mi²
Using 0.6214
That is the length factor. For area, multiply by 0.3861.
Dividing instead of multiplying
The square mile is bigger, so the number shrinks. If 100 km² became 259, you divided.
Confusing density with area
For density, use 2.59, not 0.3861, because the area is in the denominator.
Quick answers
How many square miles in a square kilometre?
0.3861.
How do I convert km² to mi²?
Multiply by 0.3861.
How many square kilometres in a square mile?
2.59.
What is 1,000 km² in square miles?
386.1 mi².
Does my number leave my device?
No. The calculation runs in your browser.
Related pages and a last word
If you work with land and area, these conversions are close at hand: Convert km² to m², Convert km² to ha, Convert acres to mi², Convert mi² to acres, Convert km to mi, Convert mi to km, Convert °C to °F, Convert °F to °C, Convert °C to K. The reverse of this page is Convert mi² to km².
In short, to convert km² to mi² multiply by 0.3861, remember that the factor is the square of 0.6214, and keep the digits your source supports. Your number stays on your device: nothing is uploaded and no account is needed.