Workers in the Washington area must earn more than twice as much today as they did in 1971 to have kept up with inflation -- and most of them don't even come close, according to a Washington Post survey.

Only two of 10 job categories studied have salary increases that pushed them ahead of the 112.6 percent rise in the cost of living here in that decade. Letter carriers and beginning lawyers appeared to be the only winners in the struggle with inflation, but the impact of higher tax and Social Security rates eroded their gains to the point where they apparently lag behind inflation along with garbage collectors, bank loan officers and teachers.

"It just gets really rough sometimes . . . more and more goes for the necessities instead of the amenities," said Michael Carroll, a Gaithersburg history teacher who does part-time jobs to supplement his $22.000-a-year regular salary.

That is about average pay for a Montgomery County teacher with 12 years' experience and a master's degree. Ten years ago the average was $13,703. If the salary had advanced at the same rate as inflation, the Montgomery average today would be $29,133 -- about $6,000 more than it is.

Other inflation losers, the survey found, include supermarket checkout clerks, police officers, GS 11 government accountants, electricians -- and members of Congress.

Salary surveys by the U.S. Bureau of Labor Statistics also indicate that wages for many workers have fallen behind the inflation rate. Wages for office clerical workers in local private businesses rose an estimated 96 percent during the last decaade; skilled maintenance workers' pay, 109 percent and unskilled plant workers, 95 percent. All those increases are less than the 112.6 percent living-cost increase for the D.C. area.

Pay for the individual worker during the last decade, of course, may vary from the averages in any survey, so that some persons are ahead of the numbers while others are behind. Also, a worker beginning a job would expect to earn considerably more money after 10 years -- even if there were no increase in the rate of inflation during that decade.

Measuring the impact of inflation on people, therefore, isn't an exact science. But The Post's survey does offer examples of what 10 years of inflation has done to 10 different jobs. And it illustrates in human terms what economists agree is the continuing loss in consumer purchasing power.

In explaining why wages have not kept up with the increase in the cost of living, economist George L. Perry of the Brookings Institution cited:

Sharp increases in energy costs, particularly gasoline, which has soared 247.6 percent since 1971.

Decline in productivity, the measure of output by workers producing goods and services in private business. U.S. productivity has been growing at a slower rate for more than a decade. In 1971, for example, productivity rose 3.6 percent over the previous year. But it declined by three-tenths of one percent in 1980 over the previous year.

Perry and other economists also say that the index overstates the inflation rate because it includes the cost of buying and financing a house, even though the average consumer does not make such a purchsae every month. It has been estimated that the housing cost, as now computed, for example, erroneously adds 1 to 2 percent a year to the index of living costs.

At the same time, however, anyone who has bought a home recently may wonder if the index understates the rate of inflation.

D.C. Police Officer Gary Hankins offers this tale of two houses: Ten years ago, when he was earning $10,000 a yer, he purchased a single-family home here for $20,000 and financed it with an 8 percent mortage. Last year Hankins, now earing nearly $21,000 a year, bought a town house. It cost nearly $60,000 and has a 14 percent mortgage.

Hankins' monthly payments have more than tripled, from $198 a month on the first house to $716 on the second. " Without my wife's salary," he said, "we couldn't have qualified for the loan.

"No question that I am worse off now than when I came into the department," Hankins said.

A breakdown of living-cost increases shows that Washington area home ownership -- which includes fuel and utilities as well as monthly payments -- now costs 138.3 percent more than it did in 1971. That is slightly less than the 138.7 percent increse in food prices but substantially more than the 116.8 percent rise in transportation costs and the 115.8 percent increase in medical expenses.

None of the seven major categories in the living-cost index has declined since 1971, although the officials who track prices say that some individual items -- such as some electronic products -- cost less today than they did 10 years ago.

One of the most dramatic examples of that countertrend is the pocket calculator, which cost more than $400 when it first appeared in retail stores in the early 1970s. Today, because of advances in technology, a basic calculator can be purchased for less than $10 in many stores. Such decreases, however, have been too isolated to overcome the increases in the total market basket of goods and services measured by the index.

Two categories that rose the least in the Washington index were apparel and upkeep, up 56.2 percent, and personal care, up 73.2 percent. That compares with the overall index increase of 112.6 percent.

Some areas of the nation have been hit harder by inflation than Washington. The average cost-of-living index for the 88 U.S. cities surveyed by the government rose by 116.2 percent over the last decade -- nearly four points more than the local increase.

In the Washington area, two workers who come close to beating inflation are the letter carrier and the freshman lawyer. But the government's bite out of their paychecks ate away their advantage. For example, a married lawyer with two children earning $15,000 a year in 1971 had $12,650 left after income tax and Social Security. To be even with inflation today, the lawyer should take home $26,788 -- about $1,000 more than he or she actually does.

Deductions for taxes and Social Security vary from one individual to another.

The salary for the lawyer in this example is based on the beginning wages for a law school graduate hired by a prestigious Washington law firm, such as Covingtgon & Burling, which competes with local and out-of-town firms for the cream of the graduating classes. The letter carrier's pay represents the average for seven years' experience.

While the young lawyer at such a firm can thank competition for pushing up wages, the postal employe must look to the union. The contract governing pay for the National Association of Letter Carriers provides increases that automatically raise the letter carrier's pay in lockstep with the cost-of-living index.

Postman James Wiggins, who delivers mail in downtown Washington, said the regular increases he gets "allow me to survive on the basic things I need, but there just isn't anything left for the luxuries of life." His annual income now is nearly $21,000 -- the top scale for most postal workers, according to the U.S. Postal Service.

Then there is the member of Congress -- who in theory is the biggest loser of the 10.

His or her salary was $42,500 in 1971. To have kept up with the 112.6 percent inflation rate, the salary should be $90,355 -- about $30,000 more than it is.

"I think the $60,000 that congressmen get now is excessive . . . so I accept $44,600," said Rep. Andrew Jacobs Jr. (D-Ind.). He said the $90,355 projection is wrong because it is tied to an inflated base.

"It all depends on when you start," he said. "I go back to 1952 for my calculations, when congressmen were paid $15,000 -- including $2,500 for expenses -- about right for their time. The inflation rate, when we checked last fall, had increased 216 percent, so the salary should be $47,400 now."

"But if you start with the big pay grab of 1969, when salaries went up 41 percent at a time of single-digit inflation, you are home free. Or should I say, 'House' free?"

Jacobs said he accepts less than the $47,400 that even his calculations indicate would be fair because "a little sacrifice is not unreasonable for a member of Congress . . . because a lot of people are out there living and eating and taking care of kids, and they are not getting $44,000."