The Washington area's 100,000-plus federal, postal and military retirees will soon be getting an inflation-triggered cost-of-living raise of 6 percent. It goes into effect March 1 and will first show up in monthly annuity checks mailed for April delivery to the more than 2 million ex-civil servants, retired military personnel and survivors of retirees.

Federal-military annuities are adjusted twice each year -- March and September -- to help retirees keep up with increased living costs. Because they are linked to inflation rather than a fixed budgetary amount, pensions of civilian and military retirees have been going up at an annual rate more than double the percentage pay increase for active duty workers.

Last September, retirees received a record 6.9 percent cost-of-living raise. In March, the boost will be 6 percent. Active duty federal workers and military personnel got a flat 7 percent pay raise in October 1979. Federal executives received 5.5 percent.

The two back-to-back pension increases will cause thousands of retirement-age civil servants, especially those in top grades, to retire shortly. As pointed out here last week, federal workers at the $50,000 pay level with more than 40 years of service can boost their annuities nearly $5,000 per year by retiring before March 1. Lower grade employes with less service may find some financial advantage be retiring in February rather than waiting until March.

Federal officials are braced for a massive wave of retirements, especially among senior-level people, between now and the end of February. Normally, between 6,000 to 8,000 people retire from Uncle Sam each month. But the last time there were similar big back-to-back cost-of-living raises to tempt large numbers of workers to retire (in June 1973), a record 50,000 people left in one day.

If you are one of the nearly 250,000-plus people eligible to retire, consider the financial options carefully. If you are one of the 900,000 not eligible to retire, watch your agency for high-level departures. This is an excellent time to move up, unless agency officials decide this is an equally excellent time to bring outsiders into middle and top jobs.