The population of Sydney is expected to increase to nearly six million people by 2036 - up 40%.
The population of New South Wales will be more than nine million people by then - an increase of 33%.
Issuing the figures in Monday, NSW planning minister Kristina Keneally said they represent an increase of 440,000 people on the 2005 projection of the state's population.
Sydney will need an extra 636,000 houses by 2031.
The ABC reports Ms Keneally said Sydney needs to continue to improve its road, its rail and its health systems.