The bad news is that it may cost more than $200,000 to bring up a child born in the early 1980s. The good news is that families of military personnel can save more than a quarter of that cost.

A recent government-sponsored study found that the average firstborn boy will cost his parents about $215,000 in today's dollars--not including college costs or the effects of inflation. That figure might be reduced by more than $55,000, however, if the family's principal wage-earner is a career soldier.

With the rising cost of living and not-so-quickly rising salaries, many military families have been grousing about the declining value of their benefits. But primarily through subsidized medical and housing costs, they can still live as well as civilian families with higher incomes.

Washington economist Dr. Lawrence Olson supervised a two-year study of the costs of childrearing funded by the National Institute of Child Health and Human Development, and then summarized the results in his book, Costs of Children (Lexington Books, 1983). He estimated the cost of raising children in military families based on information supplied by the military life-style magazine Ladycom.

To realize the full range of potential savings, military families must take advantage of Uncle Sam's benefits. Many families don't, however. For example, some pay for private medical care rather than using overcrowded and understaffed military clinics.

Furthermore, it helps to have extra stripes. The monthly Washington-area housing allowance for a service member with dependents ranges from about $320 for the lowest grade to about $820 for the highest-ranked officer.

In his original study, Olson found that even a single child can take a hefty bite out of family income. The average two-parent family with a 25-year-old principal wage-earner can expect to spend about $215,000 to raise a boy born in 1980 to the age of 22, or $149,000 if he becomes independent at age 19. The cost would rise to about $226,000 if the son attends a four-year residential private college.

The cost for a firstborn daughter is projected to be even higher: $166,000 if she becomes independent at 19, $223,000 with partial parental support through age 22 and $247,000 if she attends a residential private college. Parents tend to spend more for girls' toys, transportation, entertainment, beauty care and weddings.

Where does all this money go? The biggest bite is food: about 32 percent of the total. Other major costs are housing (31 percent), transportation (13 percent), education (13 percent), health care (7 percent) and clothing (4 percent).

For children of active-duty service members, some of these costs can be reduced significantly:

Medical Care: Children can receive free regular medical care at government clinics and hospitals, where in-patients are charged only for meals. Where such facilities are unavailable, a special insurance plan covers major costs. TOTAL ESTIMATED SAVINGS: 60 percent.

Food: Base commissaries can reduce the cost of food consumed at home by about 25 percent.

Clothing: Post exchanges discount clothing by about 20 percent, but the limited selection sometimes drives parents to shop elsewhere. TOTAL ESTIMATED SAVINGS: 10 percent.

Housing: Military parents can achieve large savings by living on their assigned bases, where the government pays for rent, utilities, and repairs. For those unable or unwilling to live in base housing the government's basic allowance for quarters (BAQ) and variable housing allowance (VHA) for high-cost areas help pick up the tab for sheltering children. TOTAL ESTIMATED SAVINGS: 50 percent, minus $250 per child per year to account for out-of-pocket expenses due to frequent moving.

Child Care: Where it's available, low-cost, on-base child care can reduce the cost of raising preschoolers. TOTAL ESTIMATED SAVINGS: 10 percent from "Other" category during years 0-4.

Transportation: Gas and air-travel discounts generally don't exceed those available to the public. NO SAVINGS.

Other: Free on-base recreational facilities, counseling and other services can cut childrearing costs by an additional 5 percent.

Education: The study assumes that children attend public schools. College education costs can be cut by up to $12,000 per year if children take advantage of military scholarship programs such as Reserve Officers Training Corps (ROTC). ROTC enrollments are currently up by 87 percent over the 1973-74 school year.

The total savings (excluding college education cost, which varies widely) reveal that instead of spending $214,957 to raise a single male child to the age of 22 without college, a military family might spend $158,995. That's a savings of $55,962, or about 26 percent.

But it's actually not that simple. Olson points out that military family benefits must be viewed as extra income. And for each extra dollar they earn, parents tend to spend about 21 cents on their children. What this means is that a military couple earning $28,000 per year should be able to provide the same amount of goods and services to their child as a civilian couple earning $40,000 per year.

While military benefits help reduce the direct costs of childrearing, the military life style can play havoc with indirect costs, such as income lost when a mother forgoes paid employment. Many military wives have trouble establishing careers due to frequent relocation, living overseas where job opportunities are scarce, and their husbands' erratic work schedules.

It also should be noted that military benefits, including lower childrearing costs, carry a price tag: the obligation to fight or prevent war. For many people, the rigors of military service can't be sweetened by any level of benefits.

Yet today's parents, although they may be more apt to have children for deep personal reasons, are not oblivious to the high cost of childrearing. By upgrading the availability and quality of family benefits, the services could further enhance their ability to attract qualified, committed new members.