President Carter yesterday called for a 9.1 percent pay raise Oct. 1 for the federal government's roughly 1 million white-collar workers, 300,000 of whom live in the Washington metropolitan area.

Carter arrived at the pay raise figure after extensive negotiations with the American Federation of Government Employes in an effort to satisfy them in this election year without outraging other voters and seeming to violate his anti-inflationary positions.

By law, federal pay is required to be kept comparable with pay scales in the private sector, but the president has latitude to interpret that.

Comparability as strictly defined by the government's controversial formula would have given workers a 13.49 percent raise this October, but Carter followed the pattern of recent years by choosing a lower number, one that is roughly equal to the administration's projection of a 9 percent inflation rate in the coming year.

The military is not affected by yesterday's decision, because Carter and Congress already have agreed on an 11.7 percent military pay raise to help fill the ranks of the all-volunteer armed forces, the first time in years military pay has been adjusted separately from civilian pay.

The percentage chosen by the president each year has an enormous effect, because many government agencies not directly affected follow the president's lead voluntarily in granting raises, as do some private-sector groups.

The American Federation of Government Employes convention in Honolulu, for example, passed a resolution pressuring D.C. Mayor Marion Barry either to give the roughly 50,000 District workers the same pay raise or enter into negotiations on pay with their union.

"A decision on pay comparability for federal civilian employes necessarily must be made in the broader context of the present economic situation in this country. Inflation is a continuing threat to the economy, and consequently we still have anti-inflationary pay standards for all pay increases, public or private," Carter said in proposing the 9.1 percent raise to Congress.

Each 1 percent increase in federal white-collar and military pay costs the government about $525 million.

The president began the year proposing a 6.2 percent pay for the white-collar federal workers. That figure, however, was pegged to a proposal to restructure the way yearly raises are calculated.

Carter proposed an overhaul of the system for calculating comparability on the grounds that it is weighed to produce an unrealistically high number. Congress did not act on his proposal, however.

A midyear budget review projected a 7.8 percent pay raise, but the federal workers' union pressed for more, and the 9.1 figure was arrived at by averaging all private-sector labor settlements from March 1979 to last March. a

The 9.1 percent raise would keep workers about even with inflation in the coming year, if administration forecasts of a 9 percent rate are correct. Most U.S. workers have lost ground to inflation in recent years.

The president's proposal must be approved by both houses of Congress. A rejection by either the Senate or House would increase the raise automatically to the 13.49 percent comparability figure.

In an election year, however, it is considered highly unlikely that many politicians of either party would want to be seen increasing the raise.

Congress has already taken its usual election-year stance of freezing its own member's payu, and the top salary for federal employes remains frozen at $50,112.

The half million blue-collar federal workers are not affected by the president's decision. Their pay is negotiated by region. The 650,000 postal workers, who negotiate their contracts with the Postal Service, also are unaffected.

Retired postal, military and federal workers will all get a previously planned 7.7 percent increase in pension payments on Oct. 1.

All small group of federal white-collar workers will get the full 13.49 percent raise, according to the White House announcement. That amount will go to all those whose pay, including the raise, would remain below $9,069 per year.

The president's decision, announced shortly after he left the White House for a weekend at Camp David before the formal kickoff of his reelection campaign on Labor Day, Monday, was denounced by the National Federation of Federal Employes, another, smaller union.

"The president has chosen the politically expedient figure, one which he feels is defensible to critics who will claim it is too high, and, at the same time, one he hopes will smooth ruffled feathers among federal workers," said James Peirce, the federation's president.