Washington's real estate boom of the 1970s almost tripled the value of its black-owned homes but quadrupled the value of houses owned and occupied by whites, according to new data from the 1980 census.

Elsewhere in the metropolitan area, the median home values of blacks rose more rapidly than those of whites, narrowing the gap between the races. But in the District, whites now own the highest-priced housing in the area and blacks own the area's lowest priced.

The new figures reflect census data on incomes reported earlier, showing that the black-white gap widened in the city and narrowed in the suburbs as middle-income black families moved there in large numbers during the 1970s.

During that decade the District's population fell by 16 percent to 638,000 with the proportion of blacks remaining steady at 70 percent. The total population of the suburbs grew by 12.6 percent to 2.4 million, with both the number and proportion of blacks more than doubling.

The figures also indicate that despite fears that rising prices may be forcing poor blacks out of the District, the city still has far more low-cost housing occupied by blacks than all of its suburbs combined.

Overall, owner-occupied houses in the District had a median value in 1980 of $68,800, the second lowest after Prince George's County among the area's major jurisdictions.

However, the median value of homes owned and occupied by D.C. whites was $135,000, the Census Bureau reported, some $36,000 to $40,000 more than in the highest-priced suburbs.

For D.C. blacks, the median value of owner-occupied homes was $55,900 in 1980, several hundred dollars less than in Arlington, the lowest of major suburbs, and almost $5,000 less than in Prince George's, which gained far more black homeowners than any part of the area in the 1970s.

For houses occupied by white homeowners in the District, median values quadrupled from $33,800 in 1970 to $135,000 in 1980, the census said, by far the greatest escalation for any group in the metropolitan area. The median value of black owner-occupied homes in the city almost tripled from $18,700 to $55,900. This was about the average rise over the decade for all owner-occupied homes throughout the area, though less than the increases reported for blacks in the suburbs.

"When you hear about those astronomical prices in the District, it's really just a pretty encapsulated area that they're talking about," said Renay Regardie, president of Housing Data Reports, a firm that keeps track of real estate market activity.

"It's the predominantly white areas west of Rock Creek Park," Regardie continued, " [and] the gentrification areas around Dupont Circle and Capitol Hill. But Anacostia has not broken loose. People aren't snatching up property there. . .there are plenty of black neighborhoods in southeast and northeast where not that much has happened."

Blacks now account for about two-thirds of the 64,419 homeowners in the District and about 10 percent of the 427,920 homeowners in the suburbs.

According to the 1980 census data, 16,155 blacks owned homes valued at under $50,000 in the District, compared to 11,798 with homes of that low value in the rest of the metropolitan area.

The value of condominiums is not included in the Census Bureau figures for owner-occupied homes.

The median value of owner-occupied condominiums in D.C. was $79,300, almost $11,000 more than D.C. owner-occupied homes. According to the census, 81 percent of the city's condos were occupied by whites.

By contrast, the median value of condos in the suburbs is much less than that of suburban homes. Except for some expensive buildings in Arlington, said Roger Wentz, chief of the housing division of the Metropolitan Washington Council of Governments, most suburban condominiums are converted, relatively low-priced garden apartments.

For renters, who account for 65 percent of all households in the District and 40 percent in the suburbs, median monthly rents ranged from $207 in D.C. up to $333 in Fairfax County.

At $184 a month, the median rent paid by D.C. blacks was $76 below that in any major suburb, of which Alexandria was the lowest. The $282 median rent for D.C. whites was $5 less than in Prince George's, the lowest-rent suburb for whites.

In 1980, there were 62,388 black D.C. households paying less than $200 a month in rent, the census said, about 6 1/2 times as many as the 9,471 who paid such low rent in the suburbs. Overall, the District had about 73,000 of the 105,000 rental units throughout the area priced at less than $200 a month.

Over the decade, median rent in D.C. went up 88 percent with rents for blacks going up slightly less than rents for whites. These increases were much less than the 97 percent average rise in the Maryland suburbs and 113 percent increase in the Virginia suburbs. Virginia, unlike D.C. and Maryland, had no rent control law during the 1970s.

Walter B. Lewis, professor of city and regional planning at Howard University, suggested that the housing cost figures reinforce other census data indicating that mostly middle-income black families, not the poor, left the District during the 1970s, while young, middle-class and upper-class white professionals moved in and older, less affluent whites died or left.

Many blacks moved to the suburbs, Lewis said, for the same reasons that whites went in the 1950s and 1960s.

"There was the belief, if not the fact, that the suburban schools are better, the housing is better, the open areas more desirable," he said."These are people who are becoming middle-class, and in the beginning they want it new, they want it first-class. They don't want to stay where they used to be poor . . . . The blacks who remain in the city have lower incomes than before."

Housing cost by itself was not the crucial factor in the move, Lewis said, though many who go to the suburbs believe they can get a better house and better neighborhood for their money than they could find in the city.

The highest-priced homes owned by blacks were in Montgomery County, with a median value of $85,600, and in Fairfax, with a median of $80,500. Fairfax tripled its number of black homeowners from 1970 to 1980. In Montgomery the number rose more than 2 1/2 times.

Among whites, the $135,000 median for owner-occupied homes in the District in 1980 exceeded that of second-place Alexandria by $36,300. Montgomery, Fairfax, and Arlington followed closely, ranging from $98,000 to $94,500. In 1970, Fairfax County had the area's most expensive houses owned by whites, with a median value of $35,500, followed by D.C., which, in turn, was less than $1,000 above Montgomery.

All of the Census Bureau figures are based on estimates of value given by homeowners in April 1980. These differ somewhat from sales prices and assessments, though D.C. tax assessors said the differences are slight.