Federal workers who anticipate layoff notices from their agencies would be well-advised to think about joining the Army, Navy or Air Force (as civilians) if they want to stay on the U.S. payroll and protect their pension rights. Defense will be hiring while much of the rest of the government is firing.

The job picture is very, very confused now because the cutback numbers Reagan will submit to Congress are reductions from estimates -- not acual job totals -- made earlier by Jimmy Carter. Reagan's plan, for instance, is to chop 43,000 non-Defense positions between now and Sept. 30, and another 40,000 during the next fiscal year. But the cuts he wants to make are jobs, not necessarily people. Many do not exist, except as paper projections left by the Carter administration.

If, for example, the government actually had to trim 83,000 positions, it would require massive RIF's (reductions-in-force) in nearly every agency. But that projected 83,000 cut is based on Carter job estimates, not on the actual number of people now on the payroll. Agency heads, personnel chiefs and budget officers must first figure out whether they are over, or under, the Carter objections (for September 1981 and September 1982 job totals) before they can decide where cuts must be made. They also must figure out the impact on operations if Congress okays program cutbacks proposed by the president.

Economic Development Administration and Office of Personnel Management are two examples of places where proposed program cutbacks may lead to RIFs. EDA has been advising workers that 200 or more employees may be let go this year because of cutbacks in contracting. The Reagan people want to wipe out much of OPM, the intergovernmental personnel arm that arranges for the interchange of federal, state and local government executives.

Backers of the program say it is an inexpensive way to provide key personnel, training or expertise from Uncle Sam (via universities or directly through the government) to states and cities. Non-fans see it as a sometimes politically motivated old-boy system that pumps money into favored universities and lets agencies exile tired or troublesome executives to faraway assignments. a

Depending on the depth of the cuts, OPM may have to RIF people. Commerce, Interior, HUD and many regulatory agencies also are faced with the prospect of some layoffs. Office of Education could be hard hit, if Congress buys administration plans to change grant programs.

While the rest of the federal establishment is due to go on a diet, Defense will be beefing up. Reagan's budget calls for 14,000 new jobs over and above those projected by Carter by the end of September, and another 10,000 during the fiscal year beginning in October. Defense will get increases over the next four years.

If the government wants to help its own people facing RIFs, and not add to the unemployment program, it ought to set up an information-referral system that would match about-to-be-fired employes with job openings in the Defense establishment. Meantime, many workers who fear the ax are putting in applications to the Pentagon.