CBO puts the Iran war at $38 billion through 1 August, $2-3 billion a month from here

The Congressional Budget Office said on 15 September that the United States war against Iran had cost the Department of Defense more than $38 billion through 1 August. If the fighting stays at recent intensity, the office expects another $2 billion to $3 billion each month. Rebuilding the munitions stockpile could take at least five years.

The 19-page note was written for Representative Brendan Boyle, the senior Democrat on the House Budget Committee. CBO said the Defense Department did not answer its questions, so the office used government databases and public reporting. The $38.1 billion figure covers munitions and equipment to be replaced, extra flying hours, other operations and higher fuel costs. It does not cover pay for the dead and wounded, veterans’ care, or damage to bases.

Munitions dominate the ledger. CBO assigned $21.7 billion to replacing what has been fired: $13.1 billion for interceptors, $7.3 billion for land-attack cruise missiles and $1.2 billion for other rounds. That mix tells the story of the war as a missile exchange. Interceptors are the expensive half because they are the rounds the United States has been using to stop incoming strikes, including around energy and shipping lanes.

Monthly cost depends on the month you pick as the template. At the intensity of May and June, CBO sees about $2 billion. At July’s intensity, about $3 billion. “Monthly costs would be higher if the conflict intensified further or DoD used expensive munitions,” the office wrote. A Pentagon inspector general report had put the bill through the end of June at $33.4 billion. Add two months at $3 billion and the two official tallies roughly meet.

Defense Secretary Pete Hegseth told the Senate the war had cost $37.5 billion. CBO is within a billion of that number, reached without Pentagon cooperation. The office also said the war would add about 0.5 percentage points to inflation into the first quarter of 2027, mainly through reduced oil and gas shipments in the Strait of Hormuz and disrupted Red Sea traffic.

The House voted 220-204 on 15 September, for a third time, to direct the president to end hostilities against Iran unless Congress authorises them. Seven Republicans joined Democrats. That resolution does not appropriate money and does not bind the president. The CBO paper is the number that will be read against that vote. It is also the number that will be read against the administration’s war spending request. Politico noted that $38 billion is already more than half of that request.

Five years to refill interceptors and cruise missiles is the constraint that outlasts any monthly burn rate. Factories cannot compress that cycle to a wartime calendar. If the war continues at $2 billion to $3 billion a month, the United States will still be paying to replace what it has already fired when the next presidential term begins. CBO has now written that down in a form Congress can put in a hearing record.