The US Congressional Budget Office (CBO) said on September 15 (local time) that the conflict with Iran has cost the US Department of War about 38 billion USD as of August 1.
According to the CBO report, the conflict began after airstrikes by the US and Israel against Iran from the end of February. Depending on the intensity of the fighting, US military spending could increase by about 2-3 billion USD per month, or even higher.
The total cost includes money to replenish used ammunition, replace equipment damaged in combat, increased fuel costs and some other expenses.
The addition of ammunition used as of August 1 is estimated to cost $21.7 billion. CBO said this is the largest expense of the US Department of War related to the conflict.
The report also noted that one of the significant impacts on US military capabilities is that the number of defensive interceptor missiles has decreased, causing reserves to be lower in the next few years.
Based on the reported number of interceptor missiles used and the total number of missiles the US Department of Defense has purchased, CBO estimates that the country may have used about 50 - 67% of the defensive interceptor missiles in its inventory since June 2025.
Previously in July, US Secretary of Defense Pete Hegseth estimated the cost of the conflict with Iran at about $37.5 billion.
In addition to military costs, CBO believes that the conflict with Iran also puts pressure on the US economy as energy prices rise. Iran's response by blockading the Strait of Hormuz - the world's important oil transportation route - has disrupted supply and created additional pressure on energy prices.
CBO forecasts that US inflation in the first quarter of next year may be 0.5 percentage points higher than the forecast given in February, while core inflation is about 0.3 percentage points higher. Increased inflationary pressure may also affect US Treasury bond interest rates.
