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Kocaeli, 
Türkiye
737,380 people lived in Kocaeli in 2025. It is the 729th largest of the world's 12,138 cities, and the 13th largest in Türkiye.
Like every city on this site, Kocaeli is counted as a built-up area seen from above rather than as a city government's territory. Why that changes the number.
Verified 2026-09-30 · 73 canaries
People · every five years · 1975 to 2050
How Kocaeli grew
Count 10 people in Kocaeli in 1975 and the same count gives 44.1 in 2025.
On the UN's projection it will have 809,921 people in 2050. It passed 250,000 people between 1985 and 1990.
projected (after 2025) · how sure the UN is: high moderate low
How to read this: one column every five years, 1975 to 2050; its height is the number of people. Hatched columns are the UN's projection. The thin strip beneath says how sure the UN is of each figure: the stronger the colour, the surer. A blank means the place was not on the UN's list of cities that year.
People · your family's years · 1975 to 2050
Kocaeli through your family’s years
Put in the years your family were born. You’ll see how many people lived in Kocaeli in each of those years, and when each of them turned 30.
Türkiye · every city · 2025
Where it is
How to read this: every dot is one of the 177 cities in Türkiye in 2025, and a dot's area is how many people live there, the biggest being Istanbul. The ringed dot in colour is Kocaeli; the grey dots are the rest. The outlines around them are neighbouring countries.
Area and built-up land · km²
How much land it covers
In 2025, Kocaeli covered 153 km², and buildings, roads and other built-up land covered 30 km² of it. That is 41 m² of built-up land for each person, about a square 6 by 6 metres. Since 1975, its built-up land has grown to 3.1 times its size, and its people are 4.4 times as many.
How to read this: pale is the whole of the city's land; the stronger square inside it is what is actually built on. The three are drawn to the same scale, so a larger square really is more land, and hatching means the year is the UN's projection rather than a count.
Of every 100 people in Türkiye
Its share of Türkiye
Of every 1,000 people in Türkiye in 2025, 8 lived in Kocaeli, which is 737,380 people.
How to read this: 1,000 squares stand for everyone in Türkiye, one square for every 1,000th person. Count the coloured ones and you have Kocaeli's share; the grey remainder live somewhere else in the country.
Ranked by people · 2025
Cities of a similar size
In the world, 2025
- 725 Dandong China738,721
- 726 Djibouti Djibouti738,192
- 727 Mexicali Mexico737,963
- 728 Saltillo Mexico737,662
- 729 Kocaeli737,380
- 730 Benxi China734,933
- 731 Nellore India732,235
- 732 Columbus United States731,335
- 733 Sahiwal Pakistan730,463
In Türkiye, 2025
- 585 Kayseri882,238
- 694 Eskisehir766,333
- 715 Mersin750,396
- 723 Şanlıurfa739,807
- 729 Kocaeli737,380
- 825 Diyarbakir660,826
- 918 Samsun594,089
- 919 Adana593,872
- 922 Van590,314
How to read this: names are in order of size, the leading number being each city's rank among all 12,138 in 2025; the bars share a scale within a list. A jump in the ranks means a city under 300,000 people, which is not given a page here.
Apparatus
Sources and method
The figures for Kocaeli are the UN's own, at five-year steps: an estimate for each of 1975 to 2025, then projection to 2050. Projected years are drawn hatched, and the UN publishes no range of uncertainty for a city. What a city means here, how the UN measures one, and why that number can differ from the one Kocaeli publishes about itself: how the figures here are put together.
Sources: UN WUP 2025 · Natural Earth · flag-icons. Every source, its licence and how to cite it →
Verified 2026-09-30 · 73 canaries