Jersey's population could reach 119,000 by 2035 if current migration policies remain unchanged, the government said.
The States of Jersey released the figure which is based on the latest data from the 2011 census.
The population model used scenarios to explain how the island could change and how much it could rise.
Chief Minister Senator Ian Gorst said there was a fine balance between controlling migration and having enough workers to support pensioners.
The States has been using the census to draw up predictions of population sizes for future housing, education and health needs.
The statistics unit said the figures are only projections and do not take into account plans to increase the pensionable age to 67 by 2031.
Senator Gorst said if it grew too much public services would struggle to cope.
"If we don't allow people to come who are going to bring jobs, who are going to bring inward investment then the dependency ratio, the number of people working to the number of people retired, if that becomes to small then we have a problem providing services to those people who are retired," he said.
The island has a surface area of 46.13 sq miles and as of June 2012 a population of 98,000.
About 700 people move to Jersey each year and about 300 people leave.