Where does half of Japan's population live?

Half of Japan's population lives on just 2.2% of its land.

Measured from the GHSL population grid (European Commission JRC, 2025) inside Natural Earth borders. How we measured this

  • The south-east side: half the population, on 21.1% of the land
  • The rest: the other half, on 78.9%

Taller columns mean more people. The dashed line is the most lopsided straight cut that still splits the population exactly in half. Data: GHSL population grid (European Commission JRC, 2025) inside Natural Earth borders.

The straight-line test

Draw one straight line across Japan so that exactly half the population is on each side. Of all the lines that do it, the most lopsided puts half of everyone on the south-east side, on just 21.1% of the land.

Now cut the land in half instead, at the same angle. That looks like the fair cut, but the south-east half ends up with 77.8% of the people. Both figures are our measurements from the GHSL population grid (European Commission JRC, 2025) inside Natural Earth borders.

That gap between how a country looks and where its people are is exactly what Slice is about.

Why Japan's population is so packed together

About three-quarters of Japan is mountains, according to Japan's land ministry. People live where the land is flat: on the plains that rivers built at the foot of the mountains, along the coast. That is where rice could be grown, and it is where the cities are today.

Most of those plains line one stretch of the Pacific coast. The Taiheiyō Belt, a chain of cities about 1,200 km long from Ibaraki, north-east of Tokyo, to Fukuoka in the south-west, is home to around 80 million people: roughly two in every three people in Japan.

Greater Tokyo alone has about 37 million people. Compare Hokkaido, the big northern island: it covers about 22% of Japan's land (83,424 km²) but is home to about 5 million people, only around 4% of the country.

Think you can do better? Try splitting Japan yourself.

Now you know where everyone lives, so this should be easy, right? In Slice you get one straight line to cut Japan's population exactly in half, and a second try if you need it. Then the country splits and the population rises in columns, to show how close you got.

Split Japan yourselfOr play today's puzzle: four new countries

Free, no sign-up. Practice never touches your daily score or streak.

Japan in Slice after a cut: the country split in two, its population rising in columns, with each side's share labelled.

How we measured this

Every figure on this page comes from the same data as the game: the GHSL population grid (European Commission JRC, 2025) inside Natural Earth borders, which estimates how many people live in each 1 km square. We draw the country on an equal-area map, so every square kilometre counts the same.

“2.2% of its land” counts the most crowded 1 km squares first, until they hold half the people. It measures how tightly people pack, which is why it comes out much smaller than maps that colour whole cities or counties. The straight-line figures test a cut at every angle, one degree apart.

Sources