President Carter has narrowed his options for an October federal pay raise to three numbers, according to top AFGE officials here. The percentage increase he will propose, they say, will be either 7.8 percent, 9.1 percent or an across-the-board 9.5 percent raise. The higher amount would boost his stock among union leaders here, and Carter's stock needs boosting within the federal work force.

In his January budget proposal, Carter recommended a 6.2 percent raise for U.S. white collar workers. He said that would be a fair amount if federal pay and fringe benefits were compared to industry. Congress did not act on Carter's pay reform plan, however, so the administration raised its U.S. salary estimate last month. The new amount for a catch-up with industry, it said, should be 7.8 percent.

Federal worker groups -- AGGE, the National Federation of Federal Employees, National Treasury Employees Union, National Association of Government Employees and the AFL-CIO -- have all demanded more. They say it will take at least 13.5 percent to equalize U.S. and private salaries. (Private pay rose an average of 9.1 percent) between March 1979 and March 1980, according to the Labor Department.)

The newest figure to surface in the October pay raise speculation is 9.5 percent. Union insiders predict Carter will go with that amount. It is seen as the minimum he can give without alienating more than 1 million white collar federal workers, and the maximum he could allow without giving conservative GOP challenger Ronald Reagan additional waste-in-government ammunition.