South Korea covers about 100,400 km² (38,800 sq mi), making it roughly the 108th-largest country in the world. That is a little smaller than Iceland or Kentucky and a little larger than Portugal, Hungary or Indiana. South Korea occupies the southern 45 per cent of the Korean Peninsula and is about 480 km from its northern border to its south coast. Its mainland is only about 300 km across. Around 51.7 million people live in that space, making it one of the most densely populated countries in the world.
South Korea Next to Places You Know
| Place | Area | Compared with South Korea |
|---|---|---|
| Indiana | ~94,300 km² | About 6% smaller |
| Portugal | ~92,200 km² | About 8% smaller |
| Hungary | ~93,000 km² | About 7% smaller |
| Iceland | ~103,000 km² | About 3% larger |
| Kentucky | ~104,700 km² | About 4% larger |
| Cuba | ~109,900 km² | About 9% larger |
| North Korea | ~120,500 km² | About 20% larger |
| Japan | ~378,000 km² | About 3.8 times larger |
The comparison with Iceland shows why size alone says little. The two are almost the same size, but Iceland has fewer than 400,000 people, while South Korea has about 130 times as many. North Korea is the larger half of the peninsula, yet has only about half South Korea's population, as our guide to how big North Korea is sets out.
A Country That Keeps Growing Into the Sea
South Korea's official area creeps upward almost every year, because the country has been reclaiming land from its shallow western and southern coasts for decades. The largest project is Saemangeum, on the west coast, where a sea wall 33.9 km long, completed in 2010 and recognised as the longest in the world, enclosed an estuary of about 400 km² to be turned into farmland, industry and a new city. Incheon International Airport was built on reclaimed land joining two islands, and much of Incheon's Songdo district stands on former tidal flats.
The west coast is ideal for reclamation because its tides are among the highest in the world. At Incheon the sea can rise and fall by around 9 m, exposing vast mudflats at low tide. Those flats are also globally important for migratory birds, and after years of loss, several of them were listed as a World Heritage Site in 2021, the Korean Tidal Flats, which has slowed new reclamation.
Mountains Take Most of the Land
About 70 per cent of South Korea is mountainous, which matters more than the headline area. The Taebaek range runs down the east side of the country like a spine, close to the coast, so the east has steep mountains and short rivers while the west has broader plains and the main river valleys. The Han flows through Seoul, and the Nakdong through Busan's hinterland. The highest peak on the mainland is Jirisan, at 1,915 m, and the highest in the country is Hallasan, the volcano that forms Jeju Island, at 1,947 m.
Those mountains are now mostly forested, which was not always so. After the Korean War, much of the country's hillside was bare from war damage and firewood cutting. A national reforestation drive from the 1960s to the 1980s replanted it, and forests now cover about 63 per cent of the land. South Korea is often cited as one of the most successful reforestation programmes of the twentieth century.
Because so much land is steep, South Koreans are crowded onto the rest. Only about a sixth of the country is cropland, and cities are packed with high-rise apartment blocks. Most of the population lives in the western lowlands and along the south coast.
Thousands of Islands
South Korea has around 3,300 islands, most of them off its jagged south-west coast, and they add a great deal to its coastline. The CIA World Factbook gives the coastline as about 2,400 km. Korean government measurements, which follow every island, give around 15,000 km. The largest island, Jeju, covers about 1,850 km² and is a World Heritage Site for its volcanic landscape and lava tubes. Far out in the East Sea lie Ulleungdo and, beyond it, Dokdo, a cluster of rocky islets of less than 0.2 km² that South Korea controls and Japan claims under the name Takeshima.
How the Peninsula Was Divided
The line that sets South Korea's size was drawn in a hurry. In August 1945, as Japan surrendered, two American officers, Dean Rusk and Charles Bonesteel, were given about half an hour to propose where US and Soviet forces should accept the Japanese surrender in Korea. Using a small wall map, they chose the 38th parallel, which put Seoul in the American zone. Separate governments were set up on each side in 1948, and in June 1950 the North invaded.
When the armistice was signed on 27 July 1953, the new line followed the front rather than the parallel. In the west it runs south of the 38th parallel, leaving the old royal city of Kaesong in the North. In the east it runs well north of it, so South Korea gained the mountains around Seoraksan and much of Gangwon province. The trade roughly balanced out in area.
The Border That Defines the Country
South Korea's only land border is not a border in the usual sense. It is the Military Demarcation Line, drawn at the 1953 armistice that halted the Korean War without a peace treaty, and it roughly follows the front line where the fighting stopped rather than the 38th parallel that divided the peninsula in 1945. Around it runs the Demilitarized Zone, about 250 km long and 4 km wide, one of the most heavily fortified borders on Earth. Because almost no one has entered it for seventy years, the DMZ has become an accidental wildlife refuge. Our guide to the Korean DMZ covers its history.
The border also means South Korea functions almost as an island. With no open land route north, all its trade and travel with the rest of the world goes by sea or air, and the country's economic geography looks outward to its ports: Busan, one of the busiest container ports in the world, Incheon and Ulsan.
Half the Country in One City Region
The most striking fact about South Korea's size is how much of it clusters around the capital. The Seoul Capital Area, Seoul plus Incheon and Gyeonggi province, holds about 26 million people, just over half the national population, on around 12 per cent of the land. To spread growth, the government built Sejong City about 120 km south as a new administrative capital, and since 2012 many ministries have moved there. Seoul remains the political and economic centre. The next largest cities, Busan with about 3.3 million people and Incheon with about 3 million, are far smaller.
The national density is about 515 people per square kilometre, one of the highest in the world for a country that is not a city-state. That is about three and a half times China's and fourteen times the United States'. The population has also started to shrink. South Korea has the lowest fertility rate in the world, 0.72 children per woman in 2023, and its population has been falling since 2020.
A Small Country With Four Real Seasons
South Korea is small, but its climate varies enough to feel much larger. Seoul has a continental climate, with January averages below freezing, around −2 °C, and humid summers averaging about 26 °C in August. Most of the country gets about 1,200 to 1,500 mm of rain a year, and roughly half of it falls in summer, during the monsoon rains called jangma from late June through July. Typhoons arrive from the Pacific in late summer and early autumn, usually hitting the south coast and Jeju hardest. In spring, winds carry "yellow dust" from the deserts of northern China and Mongolia, which can turn the sky hazy for days.
Jeju, the southernmost point, is noticeably milder, warm enough for the citrus orchards that produce the island's famous tangerines. On the mainland, winter snow is heaviest along the east coast and in the Taebaek mountains, where Pyeongchang hosted the 2018 Winter Olympics.
Seoul Itself
The capital proper is compact. The Special City of Seoul covers about 605 km², a little smaller than Singapore, and has about 9.4 million people, down from more than 10 million in the early 1990s as families moved to cheaper satellite cities in Gyeonggi. The Han River, up to about 1 km wide in the city, divides it into the older north and the newer south, including the Gangnam district, which was mostly farmland until the 1970s.
Small Distances, Fast Connections
South Korea is compact enough to cross in a morning. The KTX high-speed rail line, opened in 2004, links Seoul and Busan, about 325 km apart in a straight line, in under three hours, and most major cities are within half a day's travel of each other. The country is divided into 17 top-level administrative divisions: special and metropolitan cities, provinces, and special self-governing provinces, of which Jeju was the first. For a larger neighbour across the Korea Strait, see our comparison of how big Japan is.