The output of Australia's biggest city topped $US300 billion last financial year, comparable to economic activity of Hong Kong or Malaysia when measured in US dollars.

That would rate Sydney among the region's 10 largest economies and in the world's top 40 if it were a city-state like Singapore or an autonomous territory like Hong Kong.

Terry Rawnsley, a regional economist at consultancy SGS Economics and Planning, said the relative size and success of Australia's regional economies is underappreciated.

"Being Australians we sometimes downplay how hard we work, how smart we work, how much money we generate for ourselves," he said.

Sydney's economy grew by 4.5 per cent last financial year, the fastest rate in 15 years.

NSW's gross state product reached $US400 billion in 2015-16 making it the seventh biggest economy in Asia and the 27th largest economy in the world.

If NSW were a separate nation its economy would rank between Iran ($US412 billion) and Thailand ($US390 billion) on the international league table of economies. But consider this - NSW has only 3.8 million workers compared to Thailand's 38 million. It's a testament to the high productivity of Australian workers.

The Australian economy ranked 13th in the world in 2016 when measured in US dollars, according to International Monetary Fund estimates.

"That doesn't really get talked about much, apart from when there's a G20 meeting maybe," said Rawnsley.

"If we were the 13th-ranked soccer-playing nation in the world it would [be] a matter of national pride and acknowledgement. But being the 13th biggest economy just doesn't get the same sort of attention."

National economies are also ranked according to purchasing power parity, which takes into account the relative cost of goods and local purchasing power. On that measure the Australian economy rates 19th in the world - still far higher than our global population ranking of 53rd.

The Herald estimated how Australia's state and major city economies ranked internationally using the latest Bureau of Statistics' State Gross Product figures and estimates of capital city economies by SGS by Economics and Planning. Australia's regional economies were then compared to national economies (measured in US dollars) using the International Monetary Fund's World Economic Database.

Melbourne's $US228 billion economy was roughly equivalent to the economic output of Bangladesh, a country of 156 million people.

Victoria's economic output in US dollars was similar to that of South Africa while Queensland's is comparable to Chile.

Western Australia's economic output is close to that of Romania while South Australia's rated alongside Sri Lanka and Ethiopia. Tasmania's economy is comparable to Papua New Guinea while the output of the Australian Capital Territory is similar to Paraguay or Uganda. The North Territory's economic output is comparable to Afghanistan.

"Australia has had 100 years of industrialisation and knowledge-intensive evolution in our economy while some other countries have not yet gone as far down that path," said Rawnsley.

"We are an important player on the global stage but people forget, or maybe don't want to think about it."