Lead: A United Nations report published in November 2025 finds Jakarta’s metropolitan area now hosts an estimated 42 million people, surpassing Tokyo to become the world’s largest city by population. The World Urbanisation Prospects 2025 study applied a new, harmonised methodology to define urban extents and update global rankings. Dhaka ranks second with 37 million residents, while the Tokyo megalopolis drops to third with 33 million under the report’s criteria. The revision reflects both rapid growth in South and Southeast Asian cities and methodological changes in how cities are measured.
Key Takeaways
- Jakarta’s metro population is estimated at 42 million in the UN’s World Urbanisation Prospects 2025 report, making it the largest city by this dataset.
- Dhaka is second with about 37 million residents; metropolitan Tokyo is listed third with 33 million people under the study’s delimitation.
- The UN changed its methodology to apply consistent population and geospatial criteria, replacing earlier, varied national definitions that tended to prioritise Tokyo.
- Urban residents now make up nearly half of the world’s 8.2 billion people, versus 20% of 2.5 billion in 1950.
- The number of megacities (10 million+ inhabitants) has risen from eight in 1975 to 33 in 2025, according to the report.
- By 2050, two-thirds of global population growth is projected to occur in cities, with most of the rest in towns, amplifying urban policy challenges.
- Tokyo’s metropolitan area in the study includes Saitama, Chiba, and Kanagawa prefectures; Yokohama within Kanagawa has about 3.7 million residents.
Background
The United Nations Department of Economic and Social Affairs (UN DESA) publishes the World Urbanisation Prospects series to track long-term shifts in population distribution. The 2025 edition introduced standardized geospatial and population thresholds to delineate urban agglomerations, aiming to improve international comparability. Previous editions relied more heavily on national statistics that used differing legal or administrative definitions of cities and metro areas, producing inconsistent cross-country rankings. That inconsistency frequently placed Tokyo at the top of city population lists in earlier UN products and many external analyses.
Global urbanisation has been rapid and sustained: the share of people living in cities expanded dramatically after 1950, driven by rural-to-urban migration, natural increase, and the reclassification of built-up areas. Economic transformation, industrialisation, and education-driven migration concentrated growth in Asian and African urban centres over recent decades. National and local governments, international agencies, investors and planners increasingly rely on harmonised urban metrics to design infrastructure, housing, and climate resilience strategies. The UN’s revised approach is intended to provide a consistent baseline for those policy decisions.
Main Event
The World Urbanisation Prospects 2025 report estimates Jakarta’s urban footprint contains about 42 million people, moving it ahead of Tokyo under the study’s new delimitation rules. UN officials say the change is not a simple reversal of fortunes for Tokyo but the consequence of applying uniform geospatial criteria across countries. Under the new rules, some metro areas that were previously aggregated differently are now measured in a comparable way, reshaping the global ranking of large urban agglomerations.
Dhaka, long recognised for rapid urban growth, appears as the second-largest metro with roughly 37 million inhabitants, reflecting both population increase and metropolitan expansion. Tokyo’s 33 million in the report refer to a megalopolis that includes Saitama, Chiba and Kanagawa prefectures; the study notes that the broader Tokyo region has experienced demographic decline similar to national trends in Japan. By contrast, the area defined as “Tokyo proper”—the 23 special wards plus 26 smaller cities—has a population of just over 14 million, up from 13.2 million about a decade ago according to Tokyo metropolitan authorities.
The report also highlights longer-term patterns: urban populations have more than doubled since 1950, and the count of megacities (10 million or more) has quadrupled since the mid-1970s. UN projections cited in the study indicate that most future population growth—about two-thirds by 2050—will take place in cities, concentrating demand for housing, transport, jobs and services in already-dense metropolitan regions.
Analysis & Implications
The methodological change matters as much as the headline ranking. By harmonising spatial and population thresholds, the UN aims to reduce bias introduced when countries use divergent legal or administrative boundaries to define cities. For planners and international agencies, a consistent urban measure improves cross-city comparisons for infrastructure investment, climate adaptation and public health planning. It also shifts attention to rapidly expanding lower- and middle-income megacities, where governance and service delivery gaps are most acute.
For Jakarta and other fast-growing Asian metros, the top ranking exposes urgent policy trade-offs: managing flood risk, upgrading housing and utilities, and expanding public transit require large, sustained investments. Jakarta’s geography and subsidence issues already complicate infrastructure choices; a larger official population estimate increases the scale and cost of resilience and service provision. International finance, development partners and national governments are likely to recalibrate priorities if harmonised data become the normative benchmark.
Tokyo’s fall to third place in the new ranking does not signify a sudden decline in its urban economic role, but it underscores demographic divergence within Japan and the effect of measurement choices. Tokyo proper’s population growth—driven by young in-migrants seeking education and work—highlights an internal urban dynamism even as the broader region follows national population contraction. For investors and policy-makers, the distinction between metropolitan extents and city cores has practical implications for housing markets, transport planning and social services targeting.
Comparison & Data
| Rank | City (metropolitan area) | Estimated population (2025) |
|---|---|---|
| 1 | Jakarta | 42,000,000 |
| 2 | Dhaka | 37,000,000 |
| 3 | Tokyo (megalopolis) | 33,000,000 |
| — | Tokyo proper (23 wards + 26 cities) | ~14,000,000 |
| — | Megacities (1975) | 8 |
| — | Megacities (2025) | 33 |
The table highlights both absolute population sizes and the dramatic rise in the number of megacities since 1975. These data points illustrate how concentrated population growth has become in a relatively small set of urban agglomerations, predominantly in Asia. Policymakers need to translate such aggregated statistics into locally tailored strategies—land use, flood defences, public transit and affordable housing—to manage the social and environmental impacts of large metropolitan populations.
Reactions & Quotes
The UN’s population estimates office framed the change as methodological improvement rather than a simple chart-topper shift.
“The new assessment provides a more internationally comparable delimitation of the urban extent based on similar population and geospatial criteria.”
Patrick Gerland, Head, Population Estimates and Projections Section, UN DESA
UN leadership emphasised urbanisation as an opportunity if managed strategically.
“When managed inclusively and strategically, [urbanisation] can unlock transformative pathways for climate action, economic growth, and social equity.”
Li Junhia, UN Under-Secretary-General for Economic and Social Affairs
Tokyo authorities note a distinction between metro-area trends and population changes within Tokyo proper, highlighting recent inward migration of young people for work and study.
“Population of Tokyo’s 23 wards and neighbouring cities is just over 14 million, reflecting recent gains compared with a decade ago.”
Tokyo Metropolitan Government (official statement)
Unconfirmed
- Whether national statistical offices will fully reconcile their published administrative counts with the UN’s geospatial delimitation in forthcoming releases remains unclear.
- Short-term projections about when Jakarta’s growth will slow or stabilise are model-based and subject to migration, fertility and policy changes that are not yet settled.
Bottom Line
The UN’s revision places Jakarta at the top of its 2025 city-population list, a change driven more by harmonised measurement than by an abrupt demographic collapse in Tokyo. For planners and policymakers, the finding reframes priorities: rapidly expanding Asian megacities demand scaled investments in housing, infrastructure and climate resilience.
Adopting the UN’s standardized urban definitions will likely reshape international comparisons, funding allocations and academic research. Readers should treat the ranking as part of an evolving analytical toolkit rather than a sole arbiter of urban importance; local conditions, economic output and governance capacity remain critical complements to population figures.
Sources
- The Guardian — Jakarta overtakes Tokyo as world’s most populous city (news article)
- UN DESA, Population Division — World Urbanisation Prospects 2025 (official report)
- Tokyo Metropolitan Government — population statistics (official)
- Japan Ministry of Internal Affairs and Communications — demographic data (official)