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Cardiff, 
United Kingdom
390,692 people lived in Cardiff in 2025. It is the 1455th largest of the world's 12,138 cities, and the 17th largest in the United Kingdom.
Like every city on this site, Cardiff 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 Cardiff grew
For every 10 people in Cardiff in 1975, there were 15.1 in 2025.
On the UN's projection it will have 405,702 people in 2050.
projected (after 2025) · how sure the UN is: high moderate low
How to read this: each column is one of the UN's five-yearly estimates, 1975 through 2050, and taller means more people. Where a column is hatched the year has not happened yet. The strip under the columns is the UN's own confidence in each figure, palest where it is least sure; where it is blank the city was not on the list at all.
People · your family's years · 1975 to 2050
Cardiff through your family’s years
Put in the years your family were born. You’ll see how many people lived in Cardiff in each of those years, and when each of them turned 30.
United Kingdom · every city · 2025
Where it is
How to read this: the United Kingdom and its 150 cities in 2025, each a dot whose area is its number of people (the largest is London). Cardiff is ringed, in colour; the other cities are grey. Neighbouring countries are outlines.
Area and built-up land · km²
How much land it covers
In 2025, Cardiff covered 111 km², and buildings, roads and other built-up land covered 25 km² of it. That is 65 m² of built-up land for each person, about a square 8 by 8 metres. Since 1975, its built-up land has grown by 46%, and its people have grown by 51%.
How to read this: the outer pale square stands for all the land the city covers, and the solid square inside it for the part with buildings, roads and the like on it. All three squares share a scale, so you can compare them by eye. A hatched one is a year the UN has projected.
Of every 100 people in the United Kingdom
Its share of the United Kingdom
Of every 1,000 people in the United Kingdom in 2025, 6 lived in Cardiff, which is 390,692 people.
How to read this: shrink the United Kingdom to 1,000 people and this is what you get. The coloured squares are the ones who would live in Cardiff; the grey ones are everybody else, in other cities, in towns and out in the country.
Ranked by people · 2025
Cities of a similar size
In the world, 2025
- 1451 Corrientes Argentina392,082
- 1452 Nadiad India391,934
- 1453 Juba South Sudan391,311
- 1454 Zheba China390,709
- 1455 Cardiff390,692
- 1456 Takht Bhai Pakistan390,608
- 1457 Kassala Sudan390,525
- 1458 Wenling China390,282
- 1459 Soyo Angola389,945
In the United Kingdom, 2025
- 1137 Portsmouth488,385
- 1188 Brighton467,937
- 1262 Belfast441,925
- 1308 Coventry427,678
- 1455 Cardiff390,692
- 1473 Bournemouth386,557
- 1637 Middlesbrough349,436
- 1647 Southampton347,446
- 1728 Stoke-on-Trent332,542
How to read this: the number before each name is its place among all 12,138 cities in the world in 2025; bars are people, on one scale per list. Only cities that reach 300,000 people have a page here, so a gap in the numbers is a smaller city.
Apparatus
Sources and method
The figures for Cardiff 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 Cardiff 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