Although many federal workers feel next month's 4.8 percent raise is an insult that leaves them grazing further outside the green pastures of private industry, the small jump will raise the average white-collar bureaucrat's pay here beyond $26,000, and move metro Washington's U.S.-issue payroll within striking range of the billion-dollar-per-month mark.

Metro Washington's economy is dominated by civilian federal workers (more than 350,000 of them), military personnel and 100,000 retirees who used to be with Uncle Sam in some capacity. The monthly payroll from the civilian side of government -- excluding District of Columbia government employes -- next month will put nearly $900 million in before-taxes dollars into the local economy.

Even though U.S. executives (eight out of 10 live here) in the $50,000-plus pay range get no increases, the pay raise President Reagan has ordered -- government figures say it would take a 15-percent raise to put feds on parity with private industry workers -- will go to the vast majority of U.S. workers, nonexecutives who serve as clerks, scientists, secretaries, auditors, editors, specialists and generalists in the government's home office. The area's 22,000 blue-collar U.S. workers -- who repair government cars, design tools, repair air-conditioners and maintain buildings-- are also due a raise of around 4.8 percent in mid-month. Postal employes here, who bargain separately with their employer over wages and benefits, are just beginning to get the first round of raises, bonuses and cost-of-living increases that could boost their average salary more than $5,000 over the next three years.

Military personnel are due a raise -- amounts now under consideration by Congress. The question is not whether they will get a raise, but how much it will be. The Senate would raise pay ranging from 7 percent to 22 percent. The House is shooting for a more modest 14.3 percent across-the-board for all but top graders.

Averages (whether the statistics cover pay, weight or frequency of sex acts) can often be deceiving. But they are interesting anyhow. Consider these averages -- compiled by the Office of Personnel Management -- for various government workers as of March 31 of this year. The averages do not include any of the new pay raises. Here goes:

* Worldwide, the average white-collar U.S. worker (this does not include executives or members of Congress) got $21,832 when OPM made its March 1981 study.

* The blue-collar (wage board) average was $19,556.

* Postal pay was an average $19,088.

* The average for "other" federal workers, and this includes elected officials, VA medical personnel, Foreign Service and executives, was $26,776.

Washington area averages (as of March 1981) were:

* White collar, $25,644.

* Blue collar, $19,140.

* Postal, $20,784.

* Other, $32,766.