The U.S. war against Iran has cost the Department of Defense more than $38 billion as of August 1, according to an assessment released by the Congressional Budget Office (CBO) on September 16, 2026. The CBO estimates that costs could reach up to $3 billion per month, depending on the conflict's intensity. The report indicates that the war is expected to contribute to inflation, raising it by approximately 0.5 percentage points through the first quarter of 2027, primarily due to reduced oil and natural gas shipments through the Strait of Hormuz and shipping disruptions in the Red Sea.
The estimate aligns closely with a previous figure from Defense Secretary Pete Hegseth, who stated costs were around $37.5 billion in Senate testimony. The CBO's estimates are based on the replacement of munitions and equipment lost in combat and do not account for costs related to U.S. military personnel casualties or long-term veterans' healthcare and disability compensation.
Rep. Brendan Boyle, the top Democrat on the House Budget Committee, commented on the report, highlighting the financial burden on American taxpayers and criticizing the funding priorities of Republicans. He stated, "this nonpartisan CBO report makes clear that the war has also cost American taxpayers tens of billions of dollars and counting, while continuing to drive up costs."
The findings come as the war, which began on February 28, 2026, enters its seventh month amid ongoing concerns about its impact on voters and the economy ahead of the midterm elections. The White House requested $87.6 billion in supplemental funding in June, primarily for the war, but Congress has yet to approve this request. The CBO noted that the portion of the request related to the conflict, estimated at $42.3 billion, exceeds its own cost estimates by about 10%.
Additionally, a Pentagon inspector general report indicated that the war has led to "strategic inventory shortfalls."