Congress and the White House in the next few weeks will decide on the amount of a multibillion-dollar federal pay raise that is expected to be between 2 and 3 percent, raising the annual salary of the typical civil servant next year between $540 and $810. About 300,000 workers here and in Baltimore would get the increases.

According to private sector pay data collected by the government, civil service salaries are an average of 23 percent behind wages paid for similar jobs in the private sector. The typical white-collar federal worker here gets just over $32,000 a year, according to the Office of Personnel Management.

Nationwide, civil servants are paid an average of $27,300.

President Reagan has until midnight Monday to exercise his authority to head off the 23 percent raise -- which would cost an estimated $11.5 billion -- and instead propose the 2 percent increase he recommended in his original budget.

Congress, which can overrule the president, has tentatively approved a 3 percent raise for the more than 1.2 million white-collar federal workers, Veterans Administration medical personnel and Foreign Service staff members. Members of Congress also would get the raise.

The federal civilian payroll in the Washington area now exceeds $1.1 billion a month. That does not include pay for active duty military personnel or to government civilian or military retirees.

In January federal workers received a 3 percent raise from Congress, although the president had recommended 2 percent.

The raise does not cover postal workers or government retirees who are due a January increase based on the rise in living costs. But it would trigger increases for many firms, associations and union headquarters offices here whose pay increases follow the government pattern.

Under the complex pay law, federal workers are supposed to get October raises to bring them even with private industry. That raise is based on U.S. Bureau of Labor Statistics surveys of pay in the private sector.

Almost since the pay law started, however, presidents have rejected the big industry catch-ups. Each 1 percent white-collar federal raise costs $500 million in pay and fringes, according to OPM. A 1 percent military raise costs about $670 million.

Typically, presidents cite economic conditions for rejecting the bigger raises, or they say that the pay survey doesn't take into account pay in smaller firms and to state and local government workers and that the survey doesn't compare the value of the federal fringe package with industry.

The law gives the president an escape hatch if he sends Congress an alternate pay plan. It goes into effect unless vetoed by both the Senate and House, or unless Congress sets its own figure.

Legislation changing the effective date of pay raises from October to January expires this year. Unless it is renewed it could mean two raises next year for U.S. employes.

In 1986, Congress and the White House froze federal pay. The year before, U.S. workers got a 3 1/2 percent raise, and in 1984 workers got a 4 percent raise from Congress instead of the 3 1/2 percent recommended by the president.