Census 2016 figures released on Tuesday showed Gungahlin was Australia's second-fastest growing region, with 71,000 residents, up from 47,000 in 2011.

More than 25,000 new Canberrans arrived from overseas, seeing more than a quarter of the territory's population born outside Australia.

Despite a rocky roll-out of online census services and widespread privacy concerns, the Australian Bureau of Statistics and independent advisors said the data from August 9 was reliable and comparable to previous surveys.

New population estimates put the territory population at 406,403 people in the December quarter, up 11.2 per cent from 357,222 in 2011.

Australia's national population grew by 8.8 per cent to 23,401,892.

Experts and the Parliamentary Library expect the population growth is strong enough to see three lower house seats for the first time since the late 1990s, potentially seeing the House of Representatives grow to 151 members as South Australia loses a seat and Victoria gains one.

In Canberra the median age was 35 on census night, below the national median age of 38.

ACT residents earn about $300-per-week more than Australians nationally, with a median weekly income of $998. The ACT had the slowest wage growth in Australia, at 8.83 per cent over the past five years.

Residents pay more for housing, with the second-highest monthly mortgage repayments in Australia of $2058, a drop from $2167 in 2011.

There was a significant increase in the number of occupied private dwellings, at 142,670, an increase from 129,430 in 2011.

About 38 per cent of dwellings in Canberra are owned with a mortgage, compared with 31 per cent rented and 27 per cent owned outright. The median weekly rent of $380 remained unchanged.

Fewer Canberrans are getting married, with 37.9 per cent unmarried compared to 35 per cent nationally. There are 6.1 million families nationwide, including 46,800 same-sex couples - up by 39 per cent since 2011.

More people in the ACT identify as Aboriginal or Torres Strait Islanders, with 6508 people reporting Indigenous origins in 2016. Nationally the figure is nearly 650,000 Australians, or 2.8 per cent.

More Canberrans said they had no religious affiliations, rising from 100,764 in 2011 to 143,739 in 2016 - 36.2 per cent.

The Catholic and Anglican churches were Canberra's most popular religious groups, with 22.3 per cent and 10.8 per cent of the population respectively.

Nationally, 70 per cent of people reported having a religious affiliation.

The majority of overseas-born residents in the ACT's population were from England at 3.2 per cent, China at 2.9 per cent and India at 2.6 per cent. Kiwis made 1.2 per cent of ACT's population, with Filipinos making 1 per cent of the capital's population.

The four languages spoken most in ACT homes were English, Mandarin, Vietnamese and Cantonese, respectively; remaining unchanged since 2011.

ACT residents were the most likely to complete the troubled census process online. While more than 63 per cent of participants around Australia completed the process digitally, 81 per cent of Canberrans logged in online.

Chair of the independent assurance panel appointed by the ABS, Sandra Harding, said the figures were of comparable quality to previous census counts and "fit for purpose".

"Impacts are apparent with more people reporting age, rather than date of birth, as well as a large decline in the number of people agreeing to have their census form archived for 99 years."

Acting Chief Minister Yvette Berry said the data showed people were moving to Canberra for a high standard of living.

"Our city's population is growing because more people than ever are finding out what locals already know: Canberra is a great place to live.

"Canberrans can be proud of the direction this city is headed as we focus on building a better place to live, work, study and invest," she said.