The number Japan publishes for its own islands is 14,125. It was released on 28 February 2023 by the Geospatial Information Authority, it more than doubled the figure that had been in use since 1987, and the agency’s own question and answer page says plainly that nothing new was discovered. What changed was the rule for counting and the detail of the map.
The figure is 14,125, and the number it replaced was 6,852 from 1987
The earlier number, 6,852, was published by the Japan Coast Guard in 1987 and had been the one in general use ever since. The 2023 count came out at 14,125, and the agency attributes the gap to the advance of surveying technique rather than to any change on the ground. As mapping became more detailed, coastlines were drawn more finely, and more pieces of land became large enough to qualify under the same threshold the 1987 survey had used.
The agency states the consequence for territory in the same release: the land area of the country is measured from every piece of land in the base map, so the island count does not feed into it, and the new figure changes nothing about the country’s territory or territorial waters. It also records that the count was reconciled with the separate tally of islands that carry a territorial sea baseline, published by the Cabinet Office on 2 February 2023.
A coastline of 0.1 kilometres decides what gets counted
The counting rule is set out in three parts. First, islands recognised under legislation such as the Remote Islands Development Act and the Inhabited Border Remote Islands Act are counted once each. Second, every other piece of land drawn in the digital base map is examined, and a piece qualifies if it is enclosed by a coastline at least 0.1 kilometres long and if the agency can judge from its records that it was formed naturally. Third, land sitting in a lake or pond is excluded from both routes, the example given being Nakajima in Lake Toya.
The size of that screening job is published as a single number. The base map held 120,729 pieces of land as of January 2022, and only the pieces clearing the 0.1 kilometre threshold were put to the natural formation test at all.
What counts as land at all is settled in the agency’s annual area survey, and the rules there are narrower than they sound. The coastline used is the water line at high tide. Rivers and lakes are treated as land rather than water. At a river mouth the boundary between land and sea is drawn by joining the tips of the two banks along the natural line of the coast. Areas are measured each quarter from the same digital base map, working from latitude and longitude coordinates.
The definition of an island and the method of counting them are treated as separate questions, and the agency is explicit about which is which. The definition follows Article 121 of the United Nations Convention on the Law of the Sea, which Japan ratified in 1996. There is no international rule for the counting method, which is why the conditions above had to be set locally.
Nagasaki Airport is counted and Hakkeijima is not
The natural formation test is settled by comparing the current map against an older one, and the agency prints two worked examples side by side. Nagasaki Airport is shown against a map from 1963 and judged to be naturally formed. Hakkeijima is shown against a map from 1971 and judged not to be.
The same page shows what the 0.1 kilometre rule does to a place a visitor would describe as one island. Around Enoshima, the agency marks seven separate pieces of land, numbered one to seven, that each meet the conditions. A single named destination can therefore contribute several entries to the total.
The prefecture table adds up to 14,129, and the correction is seven islands
The prefecture breakdown is published as a one page annex, and it does not add up to the headline figure on first inspection. Adding the 47 prefecture rows ourselves gives 14,129. A final row labelled Honshu, Shikoku and Kyushu adds 3 more, taking the running total to 14,132.
The gap is explained by the annex’s own footnote. Figures in brackets are islands that straddle two prefectures, and they are included inside both prefecture figures. Ten prefectures carry a bracketed number, and those brackets add up to 14: Okayama 3, Hiroshima 2, Kagawa 2, and one each in Fukui, Kyoto, Hyogo, Yamaguchi, Tokushima, Ehime and Kochi. Fourteen bracketed entries means seven islands counted twice, so subtracting seven from 14,132 returns 14,125 exactly. That reconciliation is our own arithmetic, taken from the printed figures.
Nine prefectures are listed with no islands at all, and one of them has a coast
Nine entries in the annex read zero: Tochigi, Gunma, Saitama, Yamanashi, Nagano, Gifu, Shiga, Osaka and Nara. Eight of those nine are absent from the Meteorological Agency’s table of tsunami forecast zones, which names the coastal areas of the country. Osaka is not absent from it. Osaka Prefecture has a tsunami forecast zone of its own, and still carries a zero in the island annex.
At the other end of the same column, Nagasaki Prefecture carries 1,479, Hokkaido 1,473 and Kagoshima 1,256. Those three are the only entries above a thousand, and Nagasaki’s figure sits 6 above Hokkaido’s. Iwate is next at 861, then Okinawa at 691 and Miyagi at 666.
Honshu, Shikoku and Kyushu share a single row carrying 3
The annex ends with a row that is not a prefecture. It is labelled Honshu, Shikoku and Kyushu and it carries the figure 3. The annex prints no explanation for that row. Its three footnotes cover the data date of January 2022, the meaning of the bracketed figures, and the warning that a natural island reflects one moment and is affected by crustal movement and by surveying technique. Hokkaido has no row of its own here; the only Hokkaido figure in the table is the prefecture line of 1,473.
That small structural point is the reason the arithmetic in the previous section needs both the plus 3 and the minus 7. One is an addition for islands too big for a prefecture row, the other a subtraction for islands small enough to sit in two.
Four islands carry 95.5 per cent of the land area
Island areas come from a different publication, the area survey the same agency issues each year. The edition dated 1 July 2026 and published on 25 September 2026 gives the national land area as 377,973.68 square kilometres, and lists individual areas for every island of 1 square kilometre or more.
| Island | Area, 1 July 2026 (km²) | Share of national land area |
|---|---|---|
| Honshu | 227,942.96 | 60.31 per cent |
| Hokkaido | 77,982.32 | 20.63 per cent |
| Kyushu | 36,780.84 | 9.73 per cent |
| Shikoku | 18,295.69 | 4.84 per cent |
| Okinawa Island | 1,208.49 | 0.32 per cent |
| National land area | 377,973.68 | 100 per cent |
The four largest add to 361,001.81 square kilometres, which is 95.51 per cent of the national figure. Adding Okinawa Island takes it to 362,210.30, or 95.83 per cent. Both the sums and the percentages are ours, worked from the printed areas. That leaves 16,971.87 square kilometres for everything else, spread across the remaining 14,121 islands, and Honshu on its own accounts for a little over 60 per cent of the country.
Three further figures from the same area survey give a sense of the drop below the four: Sado at 854.81 square kilometres, Tsushima at 695.74 and Awaji at 592.44. Okinawa Island at 1,208.49 is larger than any of them and smaller than Shikoku by a factor of about fifteen, a ratio we worked out from the two printed areas. The 6 that separates Nagasaki’s island count from Hokkaido’s is likewise our own subtraction.
The published number is a floor, and it is expected to move
The agency attaches two qualifications to its own figure, and both cut in the direction of more islands rather than fewer. Land enclosed by a coastline shorter than 0.1 kilometres still meets the treaty definition of an island, so the real number is larger than the published one. And artificial land, together with naturally formed land that failed the conditions, remains part of the country’s territory whether or not it was counted.
The area figures move for reasons the agency sets out by name. Comparing 1 October 2024 with 1 October 2025, it lists coastal uplift from the Noto Peninsula earthquake, reclamation of sea surface, erosion and deposition on natural shorelines such as beaches, and changes in coastline shape caused by more detailed and more accurate map data. Three of those four are physical and one is a measurement effect, and it is the measurement effect alone that the agency names for the gap between 14,125 and 6,852.
Measuring the country is an old habit. The agency records that the national land area was first published in 1882 by the Statistical Bureau of the Grand Council of State, alongside population statistics, and that the area survey has been issued annually by prefecture and municipality since 1960. The published area feeds the population density figures in the national census and the calculation of local allocation tax.
On whether the figure will change again, the answer given is that it will. Surveying technique continues to improve, and natural islands themselves change through erosion, rising sea level and volcanic activity, so the agency says it will review the count from time to time. The 14,125 released in 2023 is therefore a reading taken at one moment with one set of instruments, not a fixed property of the country.
Sources Checked
Geospatial Information Authority of Japan — press release announcing the island count
Confirmed the release date of 28 February 2023 and the figure of 14,125; the earlier figure of 6,852 published by the Japan Coast Guard in 1987 and the attribution of the difference to more detailed mapping; the 0.1 kilometre coastline condition and the natural formation condition; the total of 120,729 pieces of land in the digital base map as of January 2022; the statement that the land area of the country is measured from all land and is unaffected; and the reconciliation with the Cabinet Office tally of islands carrying a territorial sea baseline published on 2 February 2023.
https://www.gsi.go.jp/kihonjohochousa/pressrelease20230228.html
Geospatial Information Authority of Japan — explanatory page on the number of islands in Japan
Confirmed that the definition of an island is based on Article 121 of the United Nations Convention on the Law of the Sea while no international rule governs the counting method; the three part counting method, including islands recognised under the Remote Islands Development Act and the Inhabited Border Remote Islands Act, the 0.1 kilometre coastline condition, and the exclusion of land in lakes with Nakajima in Lake Toya as the printed example; the worked examples of Nagasaki Airport against a 1963 map and Hakkeijima against a 1971 map; the seven pieces of land counted around Enoshima; and the two cautions that islands smaller than the threshold exist and that all land is territory regardless of the count.
https://www.gsi.go.jp/kihonjohochousa/islands_index.html
Geospatial Information Authority of Japan — question and answer page on the number of islands
Confirmed that land with a coastline shorter than 0.1 kilometres also meets the definition of an island; that the definition quoted is the one in the United Nations Convention on the Law of the Sea, which Japan ratified in 1996, the page printing the wording of the definition without the article number; that no new islands were discovered; that territory and territorial waters are unaffected; and that the figure is expected to change with surveying technique, erosion, sea level and volcanic activity.
https://www.gsi.go.jp/kihonjohochousa/islands_FAQ.html
Geospatial Information Authority of Japan — annex listing the island count nationally and by prefecture
Confirmed the national figure of 14,125; the 47 prefecture figures including Nagasaki 1,479, Hokkaido 1,473, Kagoshima 1,256, Iwate 861, Okinawa 691 and Miyagi 666; the nine zero entries for Tochigi, Gunma, Saitama, Yamanashi, Nagano, Gifu, Shiga, Osaka and Nara; the bracketed figures for Fukui, Kyoto, Hyogo, Okayama, Hiroshima, Yamaguchi, Tokushima, Kagawa, Ehime and Kochi; the three footnotes, covering the January 2022 data date, the statement that bracketed figures are islands straddling two prefectures and are included in both, and the warning about crustal movement and surveying technique; and the final row labelled Honshu, Shikoku and Kyushu carrying the figure 3, printed without explanation.
https://www.gsi.go.jp/common/000247634.pdf
Geospatial Information Authority of Japan — national area survey by prefecture and municipality, edition dated 1 July 2026
Confirmed the national land area of 377,973.68 square kilometres; the rule that lakes and islands of 1 square kilometre or more are listed; and the areas of Honshu 227,942.96, Hokkaido 77,982.32, Kyushu 36,780.84, Shikoku 18,295.69, Okinawa Island 1,208.49, Sado 854.81, Tsushima 695.74 and Awaji 592.44 square kilometres; the coastline being the high tide water line, rivers and lakes being treated as land and the river mouth rule joining the tips of both banks; and measurement from the digital base map using latitude and longitude coordinates.
https://www.gsi.go.jp/KOKUJYOHO/MENCHO/backnumber/GSI-menseki20260701.pdf
Geospatial Information Authority of Japan — index page for the national area survey
Confirmed the publication date of 25 September 2026 for the edition dated 1 July 2026; quarterly measurement of the areas; the four named causes of the change in national area between 1 October 2024 and 1 October 2025, published on 19 December 2025; the first publication of the national area in 1882 by the Statistical Bureau of the Grand Council of State; annual publication by the agency, by prefecture and municipality, since 1960; and the use of the published area in census population density and local allocation tax calculations.
https://www.gsi.go.jp/KOKUJYOHO/MENCHO-title.htm
Japan Meteorological Agency — boundary table for the tsunami forecast zones
Confirmed that Osaka Prefecture is listed as a tsunami forecast zone of its own, and that Tochigi, Gunma, Saitama, Yamanashi, Nagano, Gifu, Shiga and Nara do not appear anywhere in the table.
https://www.jma.go.jp/jma/kishou/know/jishin/joho/tsunami-yohoku.html
Last updated: September 2026
