Uncle Sam has been eliminating about 191 jobs a day since President Carter slapped a tough hiring freeze on most of the federal establishment in late October.

If that rate of forced attrition were to continue, the government would abolish the equivalent of a Small Business Administration or Agency for International Development each month, or get rid of enough employes to staff something the size of the Department of Transportation within a year.

Although the official body count has not been made, government manpower experts believe the first full three months of the freeze (from November through this January) should see a reduction of around 20,000 permanent, full-time jobs from the U.S. payroll. How long it can, or will, go on is anybody's guess.

Carter issued the freeze order on Oct. 25. It allows agencies -- except in rare cases -- to fill only one of every two job vacancies that occur for any reason. The freeze had little impace in October, both because it took time to filter down to agencies and also because many continued to hire people to fulfill previous job commitments.

But the hiring crunch was noticed in November and December. Officials expect the full impact of the semifreeze wll carry over at least through the rest of this month. After that, even if the 1 for 2 rule is continued, it will begin to show less dramatic results.

Veterans of past job freezes (Johnson and Nixon did it, too) say that hiring bans tend to come apart after a relatively short time. That is because agencies (and congressional friends) push for and get exemptions. Also, the normal feeral attrition rate (about three-fourths of 1 percent of the total federal population per month) always drops during a prolonged freeze.

Federal workers who normally would retire, transfer to other agencies or leave government for industry often change plans when a hiring freeze is imposed. Part of it is psychological. Also there often is a reduction in the number of "outside" jobs that make wound-be retirees or those about-to-change jobs that tight.

In addition to cutting federal employment around 7,000 jobs per month, the freeze has other interesting side effects:

Some agencies have delayed giving promotions.

There has been a significant upswing in the number of temporary and part-time employes (not covered by the freeze hired.

Many people who had counted on joining the government from college, the military or the private work force are running up against stone walls in many personnel offices.

The average grade and salary of the government work apparently is going up, even as the size of government gets smaller. Tht is because the turnover rate in lower levels and clerical jobs remains fairly heavy while the number of middle- and upper-grade employes remains constant.

If, as expected, the three-month job reduction totoals out to 20,000 or more many of the cuts President Carter will announce in his budget will, in fact, already have been made. Some agencies that, on paper, appear to be ordered to take cuts will in fact be beneath new job ceilings. If that happens, and the freeze is lifted or relaxed, there could be a modest rise in hiring again by mid-summer.

Meantime the freeze is on. If you have a good steady job, keep it.If you are looking for work, the private sector remains the best bet -- for now.