United States Defense Secretary Pete Hegseth has said that the months-long US-led war on Iran is estimated to have cost about $37.5bn so far, asking for twice that amount to continue fighting.

Hegseth provided the estimate during an intense session in Congress on Tuesday while speaking to lawmakers of the Senate Appropriations Committee (SAC), where he attempted to justify additional funding requests for a conflict that Washington claimed to have won months ago.

The new estimates are significantly higher than previous figures Trump administration officials provided between April and June.

Democrat and Republican senators grilled Hegseth and General Dan Caine, chair of the Joint Chiefs of Staff, over the cost of the war and the US’s failure to show results.

“Secretary Hegseth, despite your failure to win this war, you are back now before Congress asking for almost $70bn in additional funding,” Senator Gary Peters, a Democrat, said. “You are asking the American people for a blank cheque.”

“We need straight answers,” Republican Senator John Kennedy added during the tense questioning.

The testimony came as a June agreement between Tehran and Washington has broken down, and as the US has launched 11 consecutive nights of attacks on Iran.

The US has already racked up thousands of dollars in weapons bills since the war began on February 28, and is increasingly using up its stockpiles.

At least 18 US service members are dead, and about 500 are injured. Globally — including in the US — petrol prices and living costs are soaring.

Here’s what we know about Hegseth’s war maths:

How much has the US spent on the war so far?

Hegseth told the SAC on Tuesday that $37.5bn had been spent on the US’s war on Iran so far.

The amount is much higher than the $25bn estimate the Defense Department had given the Senate in April, during the US’s first phase of the war tagged Operation Epic Fury.

At the time, Assistant Secretary of the Army Jules Hurst III told the House Armed Services Committee that most of the costs had gone to munitions, operations, as well as equipment maintenance and replacements.

Other independent estimates put the war’s costs at about $1bn a day, reaching more than $100bn by mid-July. Trump administration officials have not provided broken-down figures.

Why is Trump asking for $67bn more?

Hegseth also told senators that the US would need an additional $67bn – nearly double the current bill – to keep up the war effort.

“He’s not making this up,” Paul Musgrave, a professor at Georgetown University in Qatar, told Global News Insight, adding that this was an unpopular war Americans did not ask for.

“The United States will need to replenish its arsenals [as] the munitions and the airframes that have been used in this conflict need to be replaced,” he said.

US President Donald Trump first requested supplemental funding from Congress earlier in June, spurring Hegseth’s testimony in the Senate.

The White House asked for $87.6bn in additional funding for the 2026 budget year. More than three-quarters of that, or $67.1bn, has been earmarked for the Department of Defense.

US weapons stockpiles are running low amid the war on Iran, investigations show, and replenishing them will take billions of dollars and between several months and several years.

Analysis by the Center for Strategic and International Studies shows that the US has used up significant numbers of its most powerful munitions on Iranian targets.

Stockpiles of at least four munitions – Patriots, THAADs, Standard Missile-3 (SM-3), and Precision Strike Missiles (PrSM) are now at 50 percent or less, compared with pre-war levels, according to the analysis.

The additional defence funding Trump’s administration has requested forms part of a $1.5 trillion budget proposal for the Defense Department for the 2027 fiscal year, according to Hegseth. The supplement will go towards weapons production and procurement, payroll, operational costs, training, and replacing damaged or lost equipment.

The 2027 defence budget, if approved by Congress, will represent a 44 percent increase in annual US defence spending and will be the highest such budget in the country’s history.

Already, US defence spending in 2026 was at a record high – $1.05 trillion. Comparatively, Washington spent $919.2bn on defence in 2025.

Hegseth, in his presentation to the SAC on Tuesday, said the additional funds and the record-high 2027 budget were a “generational investment”.

If Congress fails to approve them, the US “will face critical shortfalls that threaten our ability to pay our service members, replenish some of the equipment and munitions consumed during contingency operations and sustain vital global operations without disruption,” Hegseth warned.

What’s the cost of the Iran war to the US economy?

Aside from the direct monetary bill of the conflict, the humanitarian costs in the Middle East, the deaths and injuries to US servicemen, and the mangling of Washington’s reputation as a global superpower, the war on Iran is also painful for the domestic economy.

• Petrol pump prices shot up in the US after the war disrupted shipping in the Strait of Hormuz, where about a quarter of the world’s oil supplies transit through from Gulf countries. While per-litre petrol prices were about $2.98 before the war, some states, such as California, are seeing a nearly 100 percent price increase.
• By July 22, Americans had paid more than $72bn in extra petrol and diesel costs since the war began, according to estimates by Brown University’s Iran War Energy Cost Tracker. That amounts to $549 per household.
• Volatile oil prices have also pushed inflation to a three-year high, and interest rates are soaring, according to the Center for American Progress (CAP). The consumer price index, or the average change in prices, rose by about 4.2 percent in May, while households are expected to pay an additional $4.6bn in interest rates.

How do the Iran war costs compare with other US wars?

The US is the world’s leading spender on defence by far, and its wars, especially, are expensive.

Where the government would historically raise taxes or sell bonds to fund wars, modern wars are funded through borrowing, making their immediate effects less noticeable.

• One of the most expensive wars in modern US history remains the so-called “war on terror” that cost $8 trillion between 2001 and 2026, according to the war tracker website, War Costs. It resulted in 7,074 American deaths.
• The second world war saw Washington spend $4.1 trillion between 1941 and 1945, according to the Navy Department Library. More than 405,000 Americans died.
• The 20-year-long Vietnam War cost the US the present-day equivalent of $1 trillion and resulted in more than 58,000 American deaths.
• The war in Iraq cost $648bn by the US Navy’s estimates in 2008. Between 186,000 and 210,000 Americans were killed.
• The Afghanistan war cost $171bn by the US Navy’s estimates in 2008. More than 2,400 American troops died.