Budget office puts the Iran war at $38 billion with a $3 billion monthly tail

The Congressional Budget Office estimated the Iran war has cost taxpayers $38 billion, and said the prolonged military campaign will run at $2 billion to $3 billion a month¹. One account dates the total through July², while another describes it as the cost of the first five months of the conflict⁵.

The estimate excludes spending already budgeted for, such as the basic running costs of the military involved in the conflict³. The budget office also reported that the Department of War did not respond to its information requests, and flagged a deficit in critical munitions, including missiles⁴.

Why it matters to investors

The war has moved into the inflation forecast. The budget office put first-quarter 2027 headline PCE inflation half a percentage point above its February projection⁶, and its annual PCE inflation projection is now 0.5% higher for the first quarter of 2027⁵.

That is the transmission channel from the battlefield to the bond market: a defence outlay that runs at a few billion dollars a month is small against the deficit, but a half-point upgrade to the price forecast is not small against a central bank deciding on rates^5,6. The munitions shortfall also implies replacement procurement beyond the war itself⁴.

What to watch

Congress is contesting the authority rather than the appropriation. Lawmakers voted again to curb the president’s ability to continue military action without congressional approval, by 220 votes to 204, a result similar to earlier efforts⁸. The recurring margin suggests the question returns rather than resolves⁸.

The reporting gap is its own signal. The budget office noted that the Department of War did not respond to its information requests, so the published figure rests on what the agency could assemble independently⁴. It also excludes costs already in the budget, which means the headline number understates the total resources devoted to the campaign rather than overstating them³. Accounts of the period covered differ, with one dating the $38 billion through July and another describing the first five months of fighting^2,5.

The second variable is duration. The monthly run rate is the figure to track, because the budget office’s total is a snapshot and the campaign is described as prolonged^1,3. Iran’s supreme leader was killed in a US and Israeli strike on February 28, in an earlier phase of the same campaign⁷. Whether the monthly tail holds at the low or high end of the $2 billion to $3 billion range is what decides how much further the fiscal and inflation estimates move¹.