The Abe administration estimates that the Trans-Pacific Partnership trade pact will raise Japan's gross domestic product by ¥14 trillion by boosting exports and investment, according to sources close to the matter.
The figure represents 2.7 percent of the fiscal 2014 real GDP figure of ¥524.7 trillion.
The estimate will be presented Thursday to a task force examining the impact of the trade accord, the sources said Tuesday.
Japan, the United States and 10 other Pacific Rim countries agreed in October to create a free trade zone that will cover 40 percent of the global economy.
The administration said earlier that it will remove tariffs on 95.1 percent of farm, industrial and other imported products in value terms under the trade initiative.
In 2013, before joining talks on the deal, the government calculated that real GDP would be boosted by ¥3.2 trillion.
The latest estimate is much bigger because the positive effects of trade liberalization rules set under the pact and the impact of steps to support Japanese farmers who may suffer tougher price competition have been newly factored in, the sources said.