THE ADMINISTRATION'S economists suggest that next year's deficit currently looks as though it will be over $60 billion. That's a remarkable increase from the administration's $42.5 billion estimate only a month ago. Should you be shocked and dismayed? Should you conclude that the federal budget has once again suddenly veered wildly out of control?

No. Strange and unpredictable things sometimes happen to the federal budget, but the abrupt escalation of the 1982 budget estimate this summer is not --repeat, is not--one of them. Last March, when the Reagan budget first appeared, the Congressional Budget Office warned that it underestimated next year's spending by more than $20 billion. Nobody really doubted that the CBO was correct, but, in the politics of the budget process through the spring, it suited hardly anyone's purpose to say so. The Democratic opposition knew a higher deficit figure would only create more pressure for cutting the social programs. The administration and its congressional allies knew that a higher deficit figure would only threaten the support for the president's tax bill. There emerged a sort of tacit agreement to stick with the lower numbers, however unrealistic.

But now the tax bill has been signed into law, Congress has left town, and the administration finds it a convenient moment to go back and pick up that $20 billion understatement. In September, Congress votes its second budget resolution, in which the deficit figure becomes a legally binding limit. If it's too low, it could generate endless vexation for the White House.

Where does the $20 billion discrepancy come from? As the administration accurately explains, much of it is created by the continuation of very high interest rates. The president expected a sharp drop in rates earlier this year; the CBO did not expect it nor, for that matter, did the Senate Budget Committee. Higher interest costs will make up nearly half of that $20 billion. The rest? Tax revenues will probably run a bit low because of slow growth of the economy. There have also been some miscalculations in the costs of government.

The deficit of President Carter's 1980 budget was $60 billion. This year's deficit will be nearly as much. And now it appears likely that the deficit in Mr. Reagan's 1982 budget will be about the same. Perhap you will find that disappointing, or alarming. But it's not a surprise.