Place comparison
Koh Tao compared with Green Island: area, population and density
Koh Tao is about forty percent larger than Green Island, while Green Island reports more registered residents under its township system.
Equal-area outline comparison
Outlines are centered and scaled by official land area; position does not show geographic location.
Area
Population
Population density
Area data date
Population data date
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The guide below belongs to this pair: Koh Tao and Green Island. Change the selector above and the page follows, so the reading always matches the tool.
Direct answer
How different are Koh Tao and Green Island?
Koh Tao covers 21 km² (8.12 sq mi); Koh Tao's area is 1.39 times Green Island's. Its reported population is 2,531; Koh Tao's population is about 58.5% of Green Island's. By average density, Koh Tao's population density is about 42% of Green Island's.
Population difference
Koh Tao's population is about 58.5% of Green Island's 2,531 · 4,327Density difference
Koh Tao's population density is about 42% of Green Island's 120.4 /km² (312 /sq mi) · 286.7 /km² (743 /sq mi)Full data and sources for each place: Koh Tao area & population, Green Island area & population
Straight-line distance between geometric centres: about 2694 km; time difference: 1 hour.
On a familiar scale
- Koh Tao ≈ 36% of Manhattan (reference rung) 8,309 m² of land per resident
- Green Island ≈ 26% of Manhattan (reference rung) 3,488 m² of land per resident
Reference scales come from U.S. Census Bureau: 2025 Gazetteer Files: land area of states and counties , as of 2025-01-01.
How to read it
This is the closest new small-island comparison: both use a physical island area and a local subdistrict or township population.
Geography and shape
Both islands are compact diving destinations, but Koh Tao has about six additional square kilometres of land. A forty-percent area difference is visible on a common scale without turning either island into a regional giant.
Population context
Green Island has the larger registered population in the current sources. These are resident registers, not daily population: tourists, seasonal workers and people living without local registration can make the number present on the island very different.
Boundaries and definitions
Koh Tao uses the main-island area and Ko Tao subdistrict population, whose administration can include tiny nearby islands. Green Island uses the main island and township population. The pair is well aligned for scale, with a small remaining administrative caveat.
Koh Tao: Physical Koh Tao area paired with the 2024 Ko Tao subdistrict registered population. The administrative subdistrict also covers very small nearby islands, so density is a close local approximation rather than a headcount confined to the coastline. The ministry report the area comes from is no longer downloadable from its original address; it is cited here because it is where the figure was published, and no replacement official Thai source states an area for the island.
Green Island: Physical Green Island area paired with the registered population of Green Island Township at year-end 2025. The township and main island are nearly coextensive, but the population remains an administrative count.
In-depth guide
How should Koh Tao and Green Island be understood in context?
Koh Tao and Green Island form a useful small-island pair because their land areas are close enough for a meaningful mental comparison and both have local registered-population data.
The forty-percent land gap in practice
Koh Tao adds about six square kilometres to Green Island area. That is a visible difference, but both remain compact compared with Samui, Pha-ngan, Miyako or Ishigaki.
Coastline shape and steep terrain can make the usable road network diverge even when total area is close.
Resident density is not dive-site crowding
The calculation uses registered residents. Diving visitors, seasonal staff and temporary residents can dominate the population present on a particular day.
Use this result for settlement background, then use visitor, accommodation and transport data for operational planning.
Questions people ask
About this geographic comparison
Which is bigger, Koh Tao or Green Island?
Koh Tao is bigger, with a land area about 1.39× that of Green Island (Koh Tao 21 vs Green Island 15.1 km², or 8.12 sq mi vs 5.83 sq mi).
How big is Koh Tao compared to Green Island?
Koh Tao has 21 km² (8.12 sq mi) and Green Island has 15.1 km² (5.83 sq mi): the ratio is 1.39×. Conversely, Green Island has 71.8% of Koh Tao's area.
Does Koh Tao or Green Island have more people?
Green Island has 4,327 people (2025-12-31), versus 2,531 in Koh Tao (2024-12-31): 1.71×. In reverse, Koh Tao has 58.5% of Green Island's population. Koh Tao is 1.39× the size of Green Island — 21 km² vs 15.1 km² (8.12 sq mi vs 5.83 sq mi). Population is 58.5% as high; average density is 42% as high. Each side’s scope and reference date are set out under “Boundaries and definitions” on this page.
Is Koh Tao bigger than Green Island?
Yes. Koh Tao is bigger, with a land area about 1.39× that of Green Island (Koh Tao 21 vs Green Island 15.1 km², or 8.12 sq mi vs 5.83 sq mi). The area difference is 5.9 km². Koh Tao has 21 km² (8.12 sq mi) and Green Island has 15.1 km² (5.83 sq mi): the ratio is 1.39×. Conversely, Green Island has 71.8% of Koh Tao's area.
How much larger is Koh Tao than Green Island?
Koh Tao has about 1.39 times the land area of Green Island, or roughly forty percent more.
Which island has more registered residents?
Green Island in the current official records.
Does density show tourist crowding?
No. It divides registered residents by land area and does not count daily visitors.
Sources
- Ministry of Tourism and Sports, Thailand: Tourism-area feasibility final report
- Department of Provincial Administration, Thailand: 2024 population by subdistrict (stat_t67)
- Green Island Township Representatives Council: Geographic environment and area of Green Island Township
- Taitung County Household Registration Office: Green Island Township population and Indigenous population, December 2025
Outline data: