Loudoun County can expect to hire as many as 16 new teachers next year, at a cost of about $320,000, to handle increased course loads and enrollment resulting from new state graduation requirements, Harry E. Bibb, assistant superintendent of instruction, has told the School Board.

"We estimate we're going to need at least four and up to eight additional science teachers, at least four additional math teachers, and four additional foreign language teachers," Bibb said.

He said the average cost of hiring a new teacher in Loudoun is $20,000.

For the current year, Loudoun added 7 1/2 new teaching positions to handle the increased course load and enrollment at Broad Run High School, Bibb said.

According to the new state requirements, which begin with this year's ninth graders, students must complete 20 credits before graduating rather than 18 as before.

This will require an additional mathematics course, an additional laboratory science course, and a third additional course in either math or science. (The third course eliminates one student elective course.)

In addition, an advanced studies diploma program now available requires completion of 22 credits, including three years of math above the general level, three years of laboratory science, and three years of a foreign language or two years each of two foreign languages.

As a result, Bibb said, student enrollment this year has increased 6.4 percent in foreign languages, 4 percent in math and 11 percent in laboratory sciences.

The School Board will consider the need for new teacher positions during its deliberations over the 1985-86 school budget, which traditionally is adopted by the board in late February or early March and then sent to the Board of Supervisors for approval.

"These are upcoming budget concerns that need to be thought about, need to be absorbed. They're very real; they can't just be washed away," said Superintendent Robert E. Butt.

"It's what we asked for," he said. "We want kids to be more serious, and we've got to pay the price."