CBO puts Iran war cost to US at US$38 billion by August 1

The United States’ war with Iran had generated an estimated US$38 billion in military costs by August 1, the nonpartisan Congressional Budget Office (CBO) reported in Washington on Tuesday (September 15, 2026). Continued operations would add billions more each month.

CBO estimates put monthly costs at about US$2 billion during lower-intensity fighting and US$3 billion at the level experienced in July, with further escalation potentially costing more.

Pennsylvania Congressman Brendan Boyle, the senior Democrat on the House of Representatives Budget Committee, requested the assessment. CBO relied on public information after the Department of Defense did not respond to requests for data, leaving considerable uncertainty around the estimates.

US missile stocks could take five years to rebuild

Replacing expended munitions accounts for most of the Iran war’s direct costs, according to congressional budget analysts. Rebuilding depleted missile interceptor stocks could take at least five years.

CBO warned that reduced interceptor inventories could limit the US response to another major conflict, including one involving China and Taiwan.

Reuters reported in August that the US Army had used almost all of certain long-range precision missile stocks during the Iran campaign.

US Defence Secretary Pete Hegseth presented a US$37.5 billion estimate at a Senate hearing on July 21, when he pressed for nearly US$90 billion in emergency funding. Hegseth warned of “critical shortfalls” without the funds.

White House spokeswoman Anna Kelly defended President Donald Trump’s strikes as protecting US personnel and interests, and maintained that munitions were sufficient.

Chief Pentagon spokesman Sean Parnell also disputed the shortage findings, maintaining that the military retained sufficient resources for its missions.

Watchdog records damage to US bases and aircraft

The Pentagon’s inspector general recorded Iranian damage to hundreds of buildings at US bases across the Middle East. The watchdog also documented aircraft losses and damage involving fighter jets, refuelling aircraft and drones.

The inspector general cited an estimated US$33.4 billion in military costs through June 29, excluding infrastructure repairs. The report separately recorded about US$184 million in damage to US diplomatic facilities from Iranian strikes.

Iran war adds pressure to US inflation and debt

CBO expects annual US inflation, measured by the personal consumption expenditures price index, to be 0.5 percentage points above its pre-war forecast in the first quarter of 2027.

Attacks affecting Strait of Hormuz shipping and Gulf energy facilities have increased energy prices for consumers and producers. Before the war, roughly one-fifth of the world’s oil passed through the strait.

Recent ship and base strikes fall outside CBO’s accounting period. Borrowing costs are also excluded and could add tens of billions of dollars, Reuters reported.

US public debt passed US$40 trillion in August, adding to the fiscal pressures accompanying the conflict.

Boyle criticised the war’s human and financial costs, citing service personnel killed or wounded and the burden on taxpayers. Boyle argued that “the war has also cost American taxpayers tens of billions of dollars and counting, while continuing to drive up costs”.

Reuters had reported 18 US military deaths in the conflict by July.

Trump is working to end the war and reopen Hormuz, while contrasting Iran with the post-9/11 Iraq and Afghanistan wars. Both earlier conflicts involved more than 100,000 US troops at their peaks.

The eight-year Iraq war carried an estimated cost of about US$2 trillion. Brown University’s Costs of War project put the cost of the two-decade Afghanistan/Pakistan war zone at US$2.3 trillion. Those historical estimates include broader cost categories than the current accounting of US military operations against Iran.