The ACT Treasury believes Canberra will be home to almost 800,000 people in 40 years' time, with far more residents living in the city's north than they do now.
The government has released its latest population projections, which it uses to plan transport, health, schooling and other services.
The ACT's population is expected to rise from about 463,000 today to 784,000 in 2060.
That equates to a 1.4 per cent annual increase, marginally higher than the federal Treasury's long-term forecasts for Canberra's growth.
Overseas and interstate migration will fuel the expansion, which will mostly take place in northern districts.
At present, about 57 per cent of Canberrans live north of Lake Burley Griffin, the city's central landmark.
By 2060, that is projected to reach 65 per cent, as geographic constraints and planning preferences direct most new development northwards.
The inner north is projected to grow the most — an extra 77,000 people in 2060 compared with today — as more higher-density housing is built in the already well-established area.
The Molonglo Valley will add about 73,000 people, mostly on its northern side near Belconnen.
Belconnen, which includes the Ginninderry development to its west, is expected to gain another 69,000 residents, with Gungahlin adding 55,000.
Growth will be far more modest in the south. The inner suburbs (+26,000 people) and Woden (+17,000) will become denser, but this change will be more gradual than in the north.
The other southern districts stopped growing years ago and are expected to remain largely as they are, Treasury's report says.
"Established and relatively aged districts … like Tuggeranong and Weston Creek are either projected to shrink or grow marginally in population by 2060."
Most growth in town centres and new, undeveloped suburbs
The Treasury analysis suggests many suburbs will avoid significant change over the next four decades.
However, some established areas will transform radically.
Civic, which has fewer than 6,000 residents, is expected to become home to more than 31,000 people.
Gungahlin town centre's population will also boom, from about 8,500 today to 27,000 in 2060.
Other older suburbs projected to expand significantly include Belconnen town centre (+12,000 people), Kingston (+11,000), Phillip (+9,521), Lyneham (+8,972), Bruce (+8,650), Braddon (+7,294) and Dickson (+6,095).
The report notes Canberra's districts and suburbs have "distinct life cycles, growing quickly as land is released and new families move in, then ageing over time".
"The pattern of population growth varies across ACT suburbs based on the date that a district or suburb was first released, subsequent development activity, and finally ageing."
The ACT has been Australia's fastest-growing jurisdiction over the past decade; its relatively strong economy has lured workers from interstate and other countries.
Its population is relatively young, with a large share of residents (68 per cent) aged 15 to 64 — ages typically associated with being in the labour force.
The Treasury modelling suggests Canberra will remain a youthful, working city: its median age is projected to rise from 35 today to just 37 by 2060.
By comparison, Australia's median age is expected to be over 40 by then.
The Treasury notes that the COVID-19 pandemic made population modelling more difficult. As a result, its offered a range of projections for the ACT, from a low of 759,000 to a high of 817,000 people by 2060.
