Figures used by the Democrats Tuesday night to demonstrate that President Reagan's budget deficits are out of control may have been a little premature.

Harry C. McPherson, who narrated the Democrats' response to the State of the Union message, said that "If you take the projected deficits of the Reagan administration it comes to more than the total debt created by all other presidents in history." McPherson was a counsel to President Johnson.

But the administration's figures so far--$110.7 billion in fiscal 1982, $115 billion in fiscal 1983 and $177 billion in both fiscal 1984 and fiscal 1985--total $580 billion. The Democrats, however, claimed that the Reagan deficits would top the $725 billion net deficit accumulated from 1789 to 1981.

Sally Erickson, a staff assistant with the House Democratic Steering and Policy Committee, couldn't break down the Democrats' total. She cited a projected $196 billion deficit for fiscal 1983, but said she didn't know what figures were used for the next two years.

Stanley L. Greigg, a spokesman for the Congressional Budget Office, said, "The only way they could have come up with that higher total was to use a budget projection for current services"--that is, spending money at the same rate as the previous year. But, noted CBO budget expert Paul Van de Water, "Since everyone from Reagan to McPherson is proposing a change in spending patterns , that is not the most valid number."

The totals should change next week, though, when the president submits his fiscal 1984 budget.