In the last 22 years, prices have grown 246 percent, the population has grown 27.5 percent and the federal budget has grown about 1,000 percent.

But like much of what happens in government, part of the budget's growth is real and part is illusory.

The tremendous increase in federal spending since the budget passed the $100 billion mark in 1962 primarily is due to the creation or expansion of such entitlement programs as food stamps, Medicare and Social Security.

However, when adjusted for inflation, federal spending is about 2.3 times larger than in 1962, not 10 times.

In addition, economic growth has limited the rise in spending relative to the size of the economy. In 1962, when the gross national product was less than $550 billion, federal spending equaled 19.5 percent of GNP. Revenues were 18.2 percent of GNP, and the deficit -- a mere $7.1 billion -- was 1.3 percent.

In 1986, the GNP is expected to exceed $4.2 trillion, according to Reagan administration forecasts. Federal spending will equal about 24 percent of GNP. Revenues will be about 19 percent of GNP. And the deficit, projected to be $206 billion, will be about 5 percent of GNP if no significant deficit-reduction measures are adopted.

There also is another illusion: that when the budget equals nearly one-fourth of national income, only the remaining three-fourths is left for everyone else to spend.

In fact, about 35 percent of the budget is used to purchase goods and services. The remainder goes to pay interest on the national debt and for activities that support someone else's ability to buy goods and services, such as Social Security and revenue sharing with state and local governments.

In the sense of consuming goods and services, that therefore are not available to the rest of society, the federal government will take less than 8 percent of GNP in 1986. Of that 8 percent, three-fourths will go for national defense.

Only 2 percent of GNP will be consumed by the federal government for its nondefense payroll and its purchase of everything from paper clips to locks and dams.

Total federal purchases of goods and services equaled 11.3 percent of GNP in 1962. These purchases fell more or less steadily until they hit 7 percent in 1979. They have since climbed, primarily as the result of defense-spending increases.

Transfer payments are not consumption by the federal government but redirection of income from taxpayers to other institutions or individuals.

Many transfer programs often directly benefit the same people whose income was taxed to pay for them. The federal highway aid program transfers money to state governments for construction and maintenance of roads. Drivers pay fuel taxes and benefit from the highway improvements.

Transfer programs that help a taxpayer's elderly parents or a disabled child also may ease that taxpayer's financial obligations.

Now, much of the debate over where to cut the budget is focused on transfer programs. In 1962, they represented about 35 percent of the total budget. Now they are half.

In 1962, the Medicare, Medicaid and food stamp programs did not exist. By 1986, those programs will cost more than $110 billion, a figure greater than the 1962 budget, and 11 percent of the 1986 budget.

The largest transfer program, Social Security, will represent about 20 percent of the 1986 budget. It was 14 percent in 1962. President Reagan, who during the campaign said future Social Security benefits should not be reduced or restrained, has put the program off limits to his budget-cutters.

Interest payments on the publicly held portion of the national debt are, of necessity, also off limits. In 1986 they will be about 15 percent of the budget, up from less than 7 percent in 1962.

Social Security, interest payments and defense spending, which Reagan also says he does not want to reduce, add up to almost two-thirds of the budget. His budget team has indicated that it wants to find $50 billion in spending cuts. That would mean trimming the rest of the budget by 15 percent.

Ironically, when the budget passed the $100 billion mark, no one paid much attention because calculating Social Security spending separately kept the official budget total below that mark.

Several years later, President Lyndon B. Johnson made a point, for one last year, of holding the budget, excluding Social Security, under $100 billion.

Now Reagan is trying to hold spending under $1 trillion.