Convert mi² to km² square miles ↔ square kilometres Free Online Secure
Type a value in square miles and read it in square kilometres 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 mi² to km² (square miles ↔ square kilometres)
| mi² | km² |
|---|---|
| 1 | 2.589988110336 |
| 2 | 5.179976220672 |
| 3 | 7.769964331008 |
| 5 | 12.94994055168 |
| 10 | 25.89988110336 |
| 20 | 51.79976220672 |
| 50 | 129.4994055168 |
| 100 | 258.9988110336 |
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 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.
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.
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.
Empires, ice shelves and icebergs: very large areas, from square miles to square kilometres
History books and glaciology reports love comparisons of size: the Mongol Empire at its height covered 9 million square miles, the iceberg that broke from the Larsen C shelf in 2017 was about the size of Delaware, 2,240 square miles. Readers outside the United States and Britain think in square kilometres, so the figures need a conversion. To convert mi² to km² you multiply by 2.59: 2,240 mi² is 5,800 km², and 9.27 million mi² is 24 million km². This page multiplies as you type, and the text below shows how the biggest areas in history and nature look in both units.
Below come the rule, some worked cases, a brief look at each unit, a side by side comparison, a tour of great empires and ice masses and the slips to avoid. Everything is computed on your own device while you type.
How to convert mi² to km²: multiply by 2.59
The rule
One square mile is exactly 2.58998811 square kilometres. To convert mi² to km², multiply the square miles by 2.59. So 10 mi² is 25.9 km², 100 mi² is 259 km², 1,000 mi² is 2,590 km² and 10,000 mi² is 25,900 km². To go back, one square kilometre is 0.3861 square miles, so multiply kilometres by 0.386.
Worked examples
The Ross Ice Shelf covers 187,000 mi², 484,000 km². The Roman Empire at its greatest extent covered about 1.9 million mi², 4.9 million km². Alexander's empire reached 2 million mi², 5.2 million km². For a quick estimate, multiply by 2.5 and add 4 per cent: 100 mi² gives 250 plus 10, 260, near 259.
The square of 1.609
A mile is 1.609 kilometres, and an area is a length times a length, so the factor is 1.609 squared, 2.59. Using 1.609 on an area makes the answer 38 per cent too small, one of the most frequent slips with this conversion.
A quick check
The square mile is the bigger unit, so the number must grow about two and a half times. If your “convert mi² to km²” calculation gave you a smaller number than the square miles you began with, you divided instead of multiplying.
The square mile
One mile on a side
The square mile is 640 acres, 259 hectares or 2.59 km². It is the usual unit of area for states, counties, cities and lakes in the United States and Britain, and the base of population density in people per square mile.
Where it appears
Almanacs, atlases, news stories, census reports and weather bulletins.
The square kilometre
A thousand metres on each side
The square kilometre is a million square metres, 100 hectares or 0.386 square miles. It is the standard metric unit for countries, regions, large lakes and glaciers, and for population density in people per square kilometre.
Where it appears
Scientific papers, atlases, encyclopaedias, official statistics and news in nearly every country outside the English speaking world.
Square mile and square kilometre compared
A square mile is about two and a half square kilometres, so the number in kilometres is always larger. A region of 10,000 mi² is 25,900 km². The unit in which an area is first written affects how big it sounds, and a conversion lets you compare sources fairly.
The factor, 2.59, is easy to remember, though not round. For rough work, multiply by 2.5 and add 4 per cent. For precise work, use 2.589988.
Where the conversion appears
The great empires of history
The British Empire in 1920 covered about 13.7 million mi², 35.5 million km². The Mongol Empire at its peak 9.27 million mi², 24 million km². The Roman Empire in 117 AD about 1.9 million mi², 5 million km². The Inca Empire 770,000 mi², 2 million km². Histories in English use square miles, and a “convert mi² to km²” calculation puts them next to histories in other languages.
Ice shelves and icebergs
The Ross Ice Shelf covers 187,000 mi², 484,000 km², and the Ronne Ice Shelf 116,000 mi², 300,000 km². The iceberg A68, calved in 2017, was 2,240 mi², 5,800 km², bigger than Delaware, and the later A76 reached 1,668 mi², 4,320 km². Scientists report square kilometres, and news agencies often quote square miles.
Features on other planets
Olympus Mons on Mars has a footprint of about 113,000 mi², 295,000 km², similar to the state of Arizona. The Hellas Basin spans about 1.5 million mi², 4 million km². The Great Red Spot of Jupiter is a storm several times wider than the Earth is wide, covering tens of millions of square miles. Space articles in English use square miles for comparison with American states.
Iceberg comparisons
Journalists compare icebergs with American states or British counties. An iceberg of 1,500 mi², 3,885 km², is bigger than Rhode Island, 1,214 mi², 3,144 km². One of 300 mi², 777 km², is about the size of Hong Kong's land area. A conversion makes it possible to compare icebergs with places that readers know.
Rainforests and forest loss
The Amazon rainforest covers about 2.1 million mi², 5.5 million km². Annual forest loss of 4,500 mi², 11,650 km², is bigger than Connecticut. Reports on deforestation use square kilometres in Brazil and square miles in the American press, and the conversion bridges them.
Great plains and prairies
The North American Great Plains span about 1.4 million mi², 3.6 million km². The Eurasian steppe covers 3.5 million mi², 9 million km². The Pampas of Argentina 290,000 mi², 750,000 km². Geographers who compare grasslands across continents use whichever unit their source gives, and convert when they put them together.
Coral reefs and lagoons
The Great Barrier Reef covers 133,000 mi², 344,400 km². An atoll lagoon of 100 mi² is 259 km². Marine biologists use square kilometres in papers, while tourist leaflets in English quote square miles, so a “convert mi² to km²” calculation appears in both worlds.
National territories compared
France has 213,000 mi², 551,500 km². Germany 138,000 mi², 357,000 km². The United Kingdom 94,000 mi², 243,000 km². Italy 116,000 mi², 301,000 km². Almanacs in different countries print one or the other, and a reader switching between them has to remember the factor 2.59.
Writing both units in a text
In a text for readers in two countries, write the area in the unit of your audience first, and put the other in brackets: "5,800 km² (2,240 mi²)". Keep the same order throughout and never leave the unit out, especially in headlines, where the number often travels without the sentence.
Spreadsheet use
Write square miles in column A and =A2*2.58998811 in column B. For the reverse, use =B2*0.386102. Format with no decimals for large areas. A third column with =B2*100 gives hectares if you also need them.
Rounding
The factor is exact. For headlines, keep two or three significant figures: 2,240 mi² is about 5,800 km². For documents, keep all digits. If the source says about 2,000 mi², write about 5,200 km², never 5,179.98.
Teaching the idea
Draw a square on a map of your region, 10 miles on a side, 100 mi². Then ask how many kilometres it measures, 16.1, and how many square kilometres it covers, 259. Students see that the area grows with the square of the length factor, 1.609 squared.
Anchors worth remembering
10 mi² is 25.9 km², 100 mi² is 259 km², 1,000 mi² is 2,590 km², 10,000 mi² is 25,900 km². Texas is about 700,000 km². Rhode Island is about 3,100 km². With these anchors you can estimate any figure, and the converter above gives the exact value of a “convert mi² to km²” calculation.
Hurricane footprints and rain bands
The wind field of Hurricane Katrina covered about 90,000 mi², 233,000 km², of the Gulf Coast, and its rain bands reached further. A typical hurricane with a radius of 200 miles covers 125,600 mi², 325,000 km². Meteorologists use kilometres in Europe, miles in America, and a “convert mi² to km²” calculation ties together two reports on the same storm.
The Greenland and Antarctic ice sheets
The Greenland ice sheet covers about 660,000 mi², 1.7 million km². The Antarctic ice sheet 5.3 million mi², 13.7 million km². The area of ice is only one number: the thickness, up to 4 km, matters for volume. Glaciologists report area in square kilometres, though American sources use square miles. A “convert mi² to km²” calculation links them.
Famous comparisons: the size of Wales
British writers measure large areas in Waleses: 8,023 mi², 20,779 km². An iceberg of 4 Waleses is 32,000 mi², 83,000 km². American writers use Rhode Island, 1,214 mi², or Texas, 268,596 mi². Each comparison needs a conversion if a reader abroad is to follow, and each makes the point that very large areas are best grasped through familiar places.
Map scales and grid squares
On a map at 1:250,000, a grid square of 4 cm by 4 cm covers 10 km by 10 km, 100 km², 38.6 mi². On a US topographic quad at 1:24,000, the sheet covers about 55 mi², 142 km². Cartographers state sheet coverage in the unit of their country, and a conversion lets you compare sheets from different series.
What a conversion cannot tell you
A number in square miles or kilometres hides the shape. A region of 1,000 mi², 2,590 km², may be a compact square of 32 miles, 51 km, or a river valley 200 miles long and 5 wide. The conversion only changes units, not the geometry, so a good article gives both the area and a description of the shape.
Reading a map legend in miles
Many American maps print a scale bar in miles and a legend in square miles. To use such a map with a metric atlas, measure a distance in miles on the bar, convert it with 1.609, and square it for area. A feature that spans 3 by 4 miles covers 12 mi², 31 km², and measures 4.8 by 6.4 kilometres. The same map read in both units gives you a check against mistakes in either.
How the figures change with definitions
The area of a lake, a city or a country depends on definition: land only, land and inland water, or including territorial sea. The United States is 3.80 million mi², 9.83 million km², with water, but 3.54 million mi², 9.16 million km², of land only. The difference, 7 per cent, is bigger than any rounding in a conversion, so check the definition before comparing figures from two sources.
A quick mental routine
When you meet a figure in square miles, do three things. First, multiply by 2.5 in your head to get a rough kilometre figure. Second, compare it with something you know, such as a county or a small country. Third, run the exact conversion if the number will be printed or used in a calculation. The routine takes ten seconds and prevents both slips of scale and slips of digits.
Ancient capitals and cities
Ancient Rome inside the walls covered about 5 mi², 13 km². Constantinople inside its land walls about 5.4 mi², 14 km². Medieval Paris 1 mi², 2.6 km². Historians give urban areas in hectares or square kilometres, but works in English quote square miles, so conversions help compare cities across eras.
Battlefields and campaigns
The battlefield of Gettysburg covers about 9.5 mi², 24.6 km². The Waterloo battlefield 5 mi², 13 km². Military historians give areas in the unit of the country that preserves the site, so international comparisons need a conversion.
Medieval kingdoms and modern states
The Kingdom of Hungary in 1900 covered 125,000 mi², 324,000 km². The modern Netherlands has 16,000 mi², 41,500 km². Comparisons between states of different periods require the same unit, and the historian's default is the one of the source language.
Colonial maps and land grants
The Virginia Colony charter of 1606 gave a strip of land 400 miles long and 100 miles wide, 40,000 mi², 103,600 km². The land grant of William Penn in 1681 covered 45,000 mi², 116,500 km². Scholars of colonial history convert the grants into square kilometres to compare them with European kingdoms.
Craters, calderas and lakes of volcanic origin
The caldera of Yellowstone covers about 1,100 mi², 2,900 km². Lake Toba in Sumatra, a volcanic lake, 440 mi², 1,140 km². The Chicxulub crater has an estimated diameter of 93 miles, covering 6,800 mi², 17,600 km². Geology texts give crater areas in square kilometres, while popular accounts use square miles.
Oceans and seas by area
The Pacific covers 63 million mi², 165 million km². The Atlantic 41 million mi², 106 million km². The Mediterranean 970,000 mi², 2.5 million km². The Gulf of Mexico 600,000 mi², 1.55 million km². Maps show seas in square kilometres or square miles depending on the edition, and a “convert mi² to km²” calculation lets you compare them.
Great deserts
The Sahara covers 3.6 million mi², 9.2 million km², about the size of the United States. The Arabian Desert 900,000 mi², 2.3 million km². The Gobi 500,000 mi², 1.3 million km². Desert areas change with climate, so sources differ by ten per cent or more, a fact worth keeping in mind with any conversion.
More values for convert mi² to km²
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 mi² = 0.258999 km²
- 0.5 mi² = 1.294994055168 km²
- 3 mi² = 7.769964331008 km²
- 4 mi² = 10.36 km²
- 7 mi² = 18.1299 km²
- 15 mi² = 38.84982165504 km²
- 20 mi² = 51.79976220672 km²
- 75 mi² = 194.2491082752 km²
- 200 mi² = 517.9976220672 km²
- 500 mi² = 1,294.994055168 km²
- 2,000 mi² = 5,179.976220672 km²
- 10,000 mi² = 25,899.88110336 km²
Mistakes when you convert mi² to km²
Using 1.609
That is the length factor. For area, multiply by 2.59.
Dividing instead of multiplying
The square mile is bigger, so the number grows. If 100 mi² became 38.6, you divided.
Miles square and square miles
"Ten miles square" is 100 mi², while "ten square miles" is 10 mi². A factor of ten separates them, so read the phrase with care.
Quick answers
How many square kilometres in a square mile?
2.59.
How do I convert mi² to km²?
Multiply by 2.59.
How many square miles in a square kilometre?
0.3861.
What is 1,000 mi² in km²?
2,590 km².
Is my number sent anywhere?
No, it stays in your browser.
Related pages and a last word
If you work with land and area, these conversions are close at hand: Convert mi² to acres, Convert m² to km², Convert ha to km², Convert km² to ha, Convert km to mi, Convert mi to km, Convert °C to °F, Convert °F to °C, Convert cups to fl oz. The reverse of this page is Convert km² to mi².
To sum up: multiply by 2.59 to convert mi² to km², remember that the factor is the square of 1.609, and write the unit beside the result. The figure you enter is processed locally, with no account and no upload.