Federal agencies that may lose 16,000 jobs here (plus 130,000 more in the field) over the next two years will get special how-to-fire, when-to-furlough guidance this week from the Office of Personnel Management.

A number of nondefense units, ranging from giant departments to small regulatory agencies (some of which may have to trim one of every five workers) are considering use of RIFs (reductions in force), or furloughs, or both, to buy their way out of a budget crunch. President Reagan has directed most federal operations to cut spending 12 percent over the fiscal year that runs through next Sept. 30, and to meet lower job ceilings next year and in 1983. The combined impact of the two actions -- if Congress goes along with them -- could slash up to 75,000 jobs this fiscal year, and another 75,000 over the next two years.

OPM hopes to have the guidelines -- in the form of a five- or six-page Federal Personnel Manual letter -- ready for agencies this week so they can proceed with planning or implementing of either RIFs or furloughs. More than a dozen agencies have contacted OPM asking how they might go about putting workers on a four-day, 32-hour week once or twice a month, to save money. The federal payroll is $190 million a day, so use of furloughs could bring quick financial savings to agencies and minimize the need for RIFs, or at least massive RIFs, later on.

Some agencies hope to go the furlough route, hoping that if most or all of their workers lose a day or two of pay they can avoid layoffs. They hope the savings will carry them over until Congress and the White House resolve differences over program and spending cuts. Many of the economies Reagan has proposed are unpopular in Congress. Some of them are likely to be overruled.