MELBOURNE is the top city for students in Australia and would be number one in the world were it not for the affordability factor, according to global rankings company QS.

The Victorian capital ranks fourth in the top 50 on a new list. Sydney ranks sixth, with Brisbane at 22, Perth at 25 and Adelaide at 29.

Paris leads the table, followed by London and Boston, Vienna is number five. Australia has the most cities in the top 50.

QS head of research Ben Sowter said Australia has one of the world's most favourable study environments. "Take away the affordability factor and Melbourne would move ahead of Paris, London and Boston into first position, with Sydney not far behind," Mr Sowter said.

RMIT University vice-chancellor Margaret Gardner acknowledged fees were an impediment in the rankings. "Our dollar is affecting affordability for everyone, but we are high on the student mix factor, the truly international experience," Professor Gardner said.

University of Melbourne vice-chancellor Glyn Davis said the ranking was a welcome affirmation of Melbourne as a study destination of choice for students around Australia and the world. "The university’s attraction to international students has also continued to grow - despite a significant national downturn - with Melbourne making 40 more offers to that group through VTAC than last year," Professor Davis said.

Kusum Tamang, a Nepalese student studying for her masters in social work at RMIT, has been here three years and is unsurprised at Melbourne's primacy. "Since I first came to Melbourne I have felt like I belong here," the 24 year-old says.

"It is safe, also there are lots of things to see and do."

Her parents, who live in Kathmandu, pay part of her costs and she covers the rest with three days a week of office work.

While international students find fees, rents and transport costs high, she says, "It's absolutely worth it because we know the education we are getting makes you highly employable."

Among the QS criteria is student mix, which includes a gauge of the proportion of students who are from overseas. All Australian cities in the list scored well on this, but Melbourne had a perfect score of 100, with Perth next, on 95.

Australian cities also scored high for their academic rankings, which includes research, quality of living and employer activity. But affordability was low, with Sydney bottom of the top 50 list with 25 and Adelaide scoring the highest among the local league with 34.

Highest scoring for affordability on the global 50 were Cairo, with 96 and Mexico City with 95.

Final year RMIT journalism student David Swan, 22, says affordability is an issue for some students. "A lot of my friends are working lots of hours, or fulltime,'' he says.

Mr Swan's parents pay for his tuition under an agreement that he will repay them, but he still manages his money carefully since he opted for part-time, relatively low-paid work in journalism in preparation for next year's job hunt.

"At the moment I am editing the student newspaper, Catalyst, which pays a little bit, and writing for an IT website: [it's] not much money so it means I have to look for good deals."

Professor Gardner said: "What we know is that tertiary education is increasingly internationalised and this [ranking] is adding to the information for students. Part of the quality of education they receive is the quality of the environment in which they find themselves."

"If you are seeking an international education preparing you for a globalised marketplace you are looking for an education that supports this objective and that's what this survey of cities really [points towards]."