The Australian Bureau of Statistics says that figure comes 17 years earlier than was predicted in the late 1990s.
Experts say planning must begin immediately for a bigger Australia.
Australia has welcomed another one million people in record time.
It's been two years, nine months and two days since 23 million ticked over: now Australia's population is 24 million.
Assistant Director of Demography at the Australian Bureau of Statistics, Phil Browning, says a rise in the fertility rate, greater longevity and strong net migrations have contributed to the rapid increase.
"It's sort of a continuation of you know the Australian story. We hit half of this populaion milestone in 1968. It didn't seem so dramatic going from 12 to 24, but the next steps should be interesting, you know, what would another 24 million look like?"
That's a question which Dr Anna Boucher, lecturer on public policy and immigration at the University of Sydney, wants policy-makers to seriously consider.
Dr Boucher says planning must begin for a bigger Australia.
"Population growth is such a complex issue and you've got to have people looking at it from a transport perspective, people looking at it from an environmental perspective, people looking at it in terms of sustainability policy and rebuilding of cities and housing policy and then you've got the migration angle and I think what's happening now is that these issues are being tackled by different people in those different settings but they're not necessarily collaborating or talking to each other that effectively."
Australia's population increases by one person every minute and 31 seconds.
Overseas migration currently accounts for 53 per cent of Australia's total growth, with the remaining 47 per cent due to natural increase - or births.
Dr Boucher says migration is just one issue which politicians must carefully consider.
"Even in terms of our immigration policy, where the growth is coming from, I really don't see big-picture discussions happening about whether we should persist with that approach or whether we should streamline it more. It needs to be managed effectively from a politicial perspective because otherwise there's a concern of stratification of groups, sort of winners or losers, which can lead to social discord."
Mr Browning from the ABS says the average life expectancy for men and women has also increased.
"There's just very, very large numbers reaching age 65. The ABS is publishing those figures so I think the government, the challenge is over to them now."
If Australia's population continues to grow at 1.5 per cent per year - comparable to the rate in recent years - the bureau's population clock will reach 40 million by mid-century.
Michael Bayliss is the President of the Victorian and Tasmanian branches of Sustainable Population Australia.
He says he is concerned by the rate of population growth and believes measures must be taken to slow it.
"What we're proposing is twofold: that there is no government incentives directly for people to have large family sizes. Put that money instead into education and medical subsidies for young children instead of policies that promote large familiy sizes themselves. Also slow down non-refugee migration. We do promote that we need a very generous humanitarian intake program, but what we don't need is a socially and politically engineered population growth policies that are created pretty much purely to increase GDP."
