The charts that President Reagan used on television Monday to back up his claim that "in virtually every measure of military power the Soviet Union enjoys a decided advantage" did not tell the whole story. They left out what many arms control experts consider perhaps the most basic measure, which shows the two powers roughly in balance.

That measure is the number of individual atomic missile warheads carried by all the land-based and submarine-based missiles in each country's arsenal.

The United States and the Soviet Union each have about 7,500 of these warheads. And in fact that is the general figure the president himself uses in his strategic arms reduction talks (START) proposal calling for a one-third reduction in warheads by both sides to 5,000 apiece.

The warhead figure is very significant because that is the actual number of individual atomic explosives each country could heave at the other if all-out nuclear war broke out.

If the president had added another chart, one showing the number of bombs carried by the larger and superior U.S. fleet of long-range bombers, then the number of atomic weapons the United States could drop on the Soviet Union would be greater than the number it could drop on the United States. By next month, moreover, the U.S. Air Force will have operational its first squadron of 16 B52 bombers carrying new nuclear-tipped cruise missiles.

Each bomber will carry 12 of these missiles, which can be launched far outside Soviet air defenses and fly more than 1,500 miles to targets deep inside the country.

More than 3,000 of these new missiles are on order for the Air Force and several hundred more are to be based on ships and submarines. But they did not show up on the television screen Monday night, either.

There is no question that the Soviet Union has an enormous nuclear arsenal. The Russians do have more land-based long-range missiles (1,398) than the United States does (1,051). Theirs are also mostly newer, larger, more powerful and in some cases probably as accurate as American missiles, although nobody knows that for sure. They may also be less reliable than their American counterparts.

On the other hand, the United States has awesome power as well--certainly enough to stop anyone but a suicidal Soviet leader from even contemplating attack.

The United States has fewer but better missile-firing submarines than the Soviets. And the U.S. Navy has some 5,000 atomic warheads on its 544 undersea missiles, more than three times as many as Moscow has in its entire submarine fleet.

The American bomber fleet of 350 old B52s and 63 somewhat newer FB111s is still rated as superior to its Soviet counterpart.

The only warhead chart the president showed was an alarming one that had the Soviets with some 1,200 atomic warheads mounted on intermediate-range missiles in Europe against zero on the other side. These are missiles that can reach Europe but not span the ocean to the United States.

Not shown were the hundreds of atomic-bomb-carrying U.S. warplanes based in Europe or on aircraft carriers nearby, nor some 162 British and French missiles targeted on the Soviet Union.

Also unmentioned was the fact that the West already has in production a counter to the Soviet force. This consists of the 572 new U.S.-built Pershing II and land-based cruise missiles to be based in Europe beginning late next year. These new missiles can reach Soviet soil. In other words, it is true that Moscow has an edge in this area of weaponry, but something is already being done about it.

The president a number of times in the last two years has spoken of U.S. inferiority to the Soviets in atomic striking power. Many experienced officials, including former secretaries of defense James R. Schlesinger and Harold Brown, dispute such a stark assessment. A number of lawmakers who also disagree with that assessment have warned that it is dangerous and self-defeating to spread such a view.

On the other hand, such administration officials as Defense Secretary Caspar W. Weinberger argue that even warhead comparisons can be misleading. Weinberger notes that the B52 bombers are old, which nobody disputes, and that they would have to get through thick Soviet anti-aircraft defenses before they could drop bombs on targets inside Russia.

Yet B52s armed with cruise missiles would not have to fly through those defenses. And the Strategic Air Command crews in those bombers are highly skilled and their planes equipped with the latest electronic gadgetry. So the Soviets probably figure they can do a lot of damage, defenses or not.

Most importantly, there is little dispute that the United States will build a new bomber. In fact, the Reagan administration wants to build two of them, first 100 new B1 bombers for some $20 billion-plus and then the radar-evading Stealth for a cost that is as secret as the design.

Critics question whether both are needed. But there was no indication that either was being pursued in the president's speech, only that the B52s were older than the pilots who fly them.

Nor was much made of the undersea U.S. missile force because that is in good shape. The United States is ahead in undersea armaments and these remain the leg of the combined nuclear forces least vulnerable to Soviet attack.

The argument over land-based missiles is that Moscow could theoretically launch a first-strike with only about 25 percent of its missile force, using the ones that carries lots of warheads, and wipe out 90 percent of the 1,051 U.S. Minuteman and Titan missiles.

That, as the scenario goes, would leave only the bombers, which might get shot down en route to their targets, and the submarine missiles, which are not as accurate as their land-based counterparts, for the United States to retaliate with. The United States, therefore, might have to cave in to nuclear blackmail, it is argued.

Thus, the administration says it needs the new $26 billion MX missile in the Dense Pack formations that are supposed to keep the missiles safe and capable of retaliation. This, Reagan and Weinberger argue, will give the United States a secure deterrent; the Soviets will not start a war because they will know they can not succeed.

The argument over how much is enough for deterrence in the nuclear age is one that will probably never be settled.

What can be said with at least some certainty, however, is that a Soviet nuclear attack on the United States with an eye to knocking out our missile forces and gaining some useful advantage is on the most extreme edge of the plausible threats this country faces.

For one thing, it would require the launch with split-second precison of hundreds of Soviet missiles in a direction different from that over which they are tested. For another, it would require an assumption by Soviet leaders that an American president -- faced with the prospect that 20 million Americans would die even in an attack on the Minuteman bases -- would not push the button to launch all our missiles once warned that a Soviet attack was en route.

Do we need more insurance that this will not happen? Will the MX provide it? These are among the questions Reagan raised Monday night.