Federal agencies will get their first look today at guidelines they must follow to determine -- by October -- which functions and which employes can be shifted from Washington to the field over the next few years.

Many jobs, and a sizable chunk of the metropolitan area's $7.6 billion annual federal-military payroll, are at stake.

The Civil Service Reform Act requires a federal study (to be in President Carter's hands by fall) of Washington functions that can be shifted elsewhere. Nobody knows for sure how many federal-military personnel are here, but estimates (excluding CIA and National Security Agency job totals) indicate Uncle Sam has more than 400,000 government civilians and military people in the metro area.

More recent figures show 220,885 civilian federal workers and military personnel in the District. Metro area totals put the known number beyond 388,000.

Civilian and military personnel working for the National Security Agency at Fort Meade and the CIA in Langley, Arlington and other areas would push the federal-military population here well over 400,000.

Agencies in charge of the overall decentralization study are the Office of Personnel Management, Office of Management and Budget and General Services Administration.

The 10-page guidelines to be published today in the Federal Register will advise agencies of procedures they must follow, and criteria to be used to determine which operations might be moved from here to other cities.

Any large-scale shift of civilian and military functions from Washington would, naturally have a tremendous impact on the local economy that now benefits from about $7.6 billion a year in government and military paychecks.