New data from the Australian Bureau of Statistics shows a newborn girl in Australia has a life expectancy of 84.6 years, while for boys it is 80.4.

For girls there has been a slight improvement in life expectancy compared to the bureau's estimates from last year, but for boys the figure has remained static.

Life expectancy for both sexes has increased by about five years compared with figures from 20 years ago, when a newborn girl could expect to reach 81.1 and a boy could expect to live to 75.2.

The data shows that life expectancy in Australia varies significantly across states and territories. The ACT had the highest life expectancy for both men (81.3 years) and women (85.2 years).

But those born in the Northern Territory have a life expectancy that is about five years lower than the national projections. A newborn boy there is expected to live to 75.6, while a woman is expected to reach 78.7.

The director of the Centre for Health Policy at the University of Melbourne, Philip Clarke, said improved life expectancy in the ACT was tied to better education levels and income of its inhabitants, while shorter lifespans in the Northern Territory were connected to Indigenous disadvantage.

The data also provides estimates on the expected number of years left for every age group.

For example, a 25-year-old man can expect to live another 56 years, while a 25-year-old woman can expect to live another 60 years.

The data estimates that a 40-year-old Australian man is at the exact midpoint of his life, while 43-year-old woman is at the midpoint of hers.

But it is likely the bureau's figures underestimate average life expectancy.

Professor Clarke said the bureau used current mortality rates to project the life expectancy of a hypothetical newborn and did not factor in any future improvements in lifespan.

"If we extrapolate past trends, people can expect to live for longer," he said.

But he said growing antibiotic resistance and increasing obesity rates could impact on future life expectancy estimates.