Salaries in private sector white-collar jobs rose between 4.2 and 9.7 percent--the smallest gains in several years--in the 12 months that ended in March, the Bureau of Labor Statistics reports. Uncle Sam takes the measurements annually to help peg civil servants' salaries, more or less, to the going rate outside government.

BLS measures wages paid in professional, administrative, technical and clerical jobs in the private sector. By law, the BLS salary data provides the raw material used to determine how much of a catch-up- with-industry pay adjustment is due each October for the government's 1.4 million white-collar workers, including 360,000 in the Washington-Baltimore area.

Although the data has not yet been analyzed by the president's pay agents (the secretary of labor and the directors of the Office of Management and Budget and Office of Personnel Management), it is expected to show that U.S. workers would be due a raise in excess of 20 percent this year.

Based on the BLS survey in 1982, federal white-collar workers were told they were due an October pay raise of 18 1/2 percent. But the president, using authority he has under the pay law, recommended--and the employes got--4 percent instead.

Since the Comparability Pay Act of 1970, presidents frequently have ordered a lower pay raise than that indicated by the BLS data.

Because of the pattern of less-than-comparability raises, federal unions (and the government's own pay data) say that typical U.S. civilian employes were paid much less than their counterparts in the private sector, especially in middle- and upper-level jobs.

Both the Carter and Reagan administrations have argued that the BLS survey is too narrow to reflect the true pay picture because it excludes many small firms, and does not consider pay rates for state and local government employes. Both Carter and Reagan have also argued that the full government compensation package--retirement, vacation and other fringe benefits--should be matched against total compensation in industry.

If U.S. workers got a full raise this year based on the BLS data--and that isn't likely--they would be due an increase of as much as 24 percent. But President Reagan already has said he will not recommend any pay raise this year. The compromise budget worked out by the Senate and House calls for a 4 percent white-collar federal pay raise to be effective this January.

Here are the pay ranges BLS found in its private industry survey:

Accountants, from $19,519 to $67,919.

Auditors, $18,723 to $34,091.

Public accountants, $18,669 to $29,134.

Attorneys, $28,119 to $84,917.

Personnel directors, $32,678 to $62,645.

Chemists, $21,365 to $60,471.

Engineers, $25,556 to $66,938.

Engineering technicians, $15,646 to $28,320.

Computer operators, $12,481 to $25,206.

Photographers, $20,439 to $26,815.

Accounting clerks, $11,190 to $19,455.

File clerks, $9,702 to $13,699.

Key entry operators, $12,583 to $15,066.

Messengers, $10,915.

Personnel clerks, $12,898 to $20,198.

Purchasing assistants, $14,827 to $24,064.

Secretaries, $14,732 to $23,137.

Stenographers, $16,307 to $19,367.

Typists, $11,428 to $15,085.