The Congressional Budget Office (CBO), a non-partisan federal agency that provides economic and budgetary analysis, has estimated that the U.S. war against Iran has cost $38 billion since it began. This figure was released in a report on September 15, following a request from several Democratic members of Congress. The CBO's calculations are based on data up to early August and include expenses such as ammunition, equipment, and fuel for the military. The report highlights how the cost of the war could change depending on the conflict’s intensity. If the fighting slows down, the U.S. would still spend an additional $2 billion per month. However, if the war escalates—as it has recently—the cost could jump to $3 billion per month. The CBO noted that the cost of replacing the ammunition used in the conflict since February 28 alone totals $21.7 billion. Another concern raised by the CBO is the rapid depletion of interceptor missile stockpiles. By comparing the cost of these missiles with the number purchased, the agency estimates that the U.S. has likely used between half and two-thirds of its stock since June 2025. This raises concerns about the availability of critical defense systems in future conflicts. The CBO’s findings come after a report by the Pentagon’s Inspector General confirmed a shortage of ammunition related to the war in Iran. This report contradicted the Trump administration’s reluctance to acknowledge such shortages in recent months. Earlier in July, Defense Secretary Pete Hegseth had estimated the war’s cost at $37.5 billion, close to the CBO’s updated figure.