United States Defense Secretary Pete Hegseth has clashed with American lawmakers over the cost of war on Iran in his first appearance on Capitol Hill since the conflict – now into its third month – broke out.

The Pentagon told a hearing of the House Armed Services Committee on Wednesday that the US had spent $25bn on its war on Iran, largely on munitions and equipment maintenance.

But Democratic leaders and several economists believe that number to be a significant underestimate. They say the actual cost to the US economy and the country’s 330 million people could amount to between $630bn and $1 trillion.

“The biggest challenge, the biggest adversary we face at this point are the reckless, feckless and defeatist words of Congressional Democrats and some Republicans,” Hegseth lashed out at lawmakers who questioned US President Donald Trump’s handling of the conflict in the Middle East.

As the US-Israel war on Iran drags on, with no agreement in sight, the Trump administration has asked for a $1.5 trillion defence budget for next year – a 42 percent increase, or the largest expansion in military spending since World War II.

So, how much is the war on Iran costing the US, and does the answer depend on whose perspective matters more?

What did the Pentagon reveal on Capitol Hill?

The back and forth at the hearing on Capitol Hill took place amid growing pushback that the Trump administration has faced about the lack of transparency over Iran war spending.

The Pentagon’s acting comptroller, Jay Hurst, who testified alongside Hegseth and Joint Chiefs of Staff Chairman Dan Caine, told the committee’s top Democrat from Washington, Adam Smith, about the estimated figure of $25bn.

“We will formulate a supplemental [on additional funding], through the White House, that will come to Congress once we have a full assessment of the cost of the conflict,” Hurst said, promising to also provide a cost breakdown later.

The estimated figure only reflects “the costs of the war”, Hurst said, explaining: “We’re factoring in costs of munitions expended in that total and other operational costs.”

In March, Pentagon officials had told Congress that the war cost $11.3bn in the first six days. The estimated figure by the Pentagon is also significantly smaller than the $200bn requested by the Trump administration initially for the war.

Since February 28, US-Israeli attacks on Iran have killed at least 3,375 people, according to the Ministry of Health in Tehran. The US military has confirmed 14 combat-related deaths among its service members, with more than 200 injuries.

Did Democrats buy it?

Democrats questioning Hegseth and his associates were not buying the responses on the cost of the Iran war.

Representative Ro Khanna stated that the cost of the war was well above the Pentagon’s estimated $25bn figure. “Do you know how much it will cost Americans in terms of their increased cost in gas and food over the next year because of Iran?” Khanna asked.

As the US continues with its blockade of Iranian ports, and Tehran controls the Strait of Hormuz, gas prices in the US have hit a new high at $4.23 a gallon – the highest since 2022, when Russia invaded Ukraine. The Brent crude benchmark has been trading above $120.

The 40 percent rise in gas prices, compared with before the war, has led to the president’s approval rating hitting a record low in his second term, according to a Reuters/Ipsos poll released earlier this week. Only 22 percent of Americans approved of Trump’s handling of the cost of living.

Khanna claimed the war would cost about $631bn – or some $5,000 per household – to the US economy due to increased gas and food prices.

“You don’t know what we paid in terms of the missiles that hit the Iranian school. You don’t know what we’re paying in terms of gas. You don’t know what we’re paying in terms of food,” Khanna told Hegseth. “Your $25bn number is totally off.”

Linda Bilmes, a leading Harvard economist, has predicted that the total cost of the war could amount to $1 trillion.

What are the other costs of war besides bombs, missiles?

The US claimed earlier that it struck more than 13,000 targets over the first 39 days of fighting with Iran, before a fragile ceasefire came into effect.

For context, the US fired more Patriot missiles in the first four days of the Iran war than it supplied to Ukraine over the past four years. Each of those missiles in the defence system costs $4m — and they were shooting down Iran’s Shahed drones worth not more than $50,000 each.

However, the economics and impact of the war travel well beyond the worth of bombs and missiles.

One of the major expenses is reconstructing and repairing damaged assets.

After the US-Israeli strikes assassinated former Supreme Leader Ali Khamenei on the first day of war, Tehran initially responded by firing salvoes of missiles and drones on US military facilities and embassies in the Gulf region.

Iranian strikes caused damage to the US military camps in Kuwait, alongside other military bases like al-Dhafra airbase and Al Ruwais military base in the United Arab Emirates, Prince Sultan Air Base in Saudi Arabia, and Muwaffaq Salti Air Base in Jordan.

Earlier this month, NBC News quoted six US officials noting that Iran damaged US military bases and equipment in the Middle East far worse than publicly acknowledged. The damages alone could lead to billions of dollars in repairs.

Another report by The New York Times estimated that mere repairs to the US Navy Fifth Fleet headquarters in Bahrain could cost $200m alone.

Hegseth declined to say whether that figure included repairing damage to US bases. During budget briefings last week, Hurst, the acting Pentagon comptroller, told reporters that Washington does not “have a final number for what the damage is to our installations overseas”.

He added that the department is still assessing “what we want to construct in the future”, when asked about the cost of repairing the facilities damaged in the Iran war.

“Our partners also might contribute a share for that construction,” Hurst added. Meanwhile, economists believe that the US bill would further hike if Washington is asked by its allies in the Gulf to contribute to its own repairs from Iranian attacks.

What else costs in war other than fighting?

Bilmes, Harvard Kennedy School public finance professor, had estimated in February 2006 that the Iraq war would cost the US $3 trillion. Then, the George Bush administration was telling the US public that the fighting would cost $50bn.

Twenty years later, Bilmes ended up with among the most accurate predictions. The Iraq war’s total cost is now estimated at $2 trillion, though Bilmes believes the actual cost was higher.

“Wars always cost more than expected. Throughout history, those who get into wars tend to be optimistic about the cost and about the length of time it will take,” Bilmes told the Harvard Kennedy School in an interview.

“It is hard to measure the exact cost. But based on what we know now, it [the current Iran war] is costing about $2bn a day in short-term, upfront costs, which is the tip of the iceberg,” she said.

Apart from the short-term expenses of the war, Bilmes noted that the long-term expenses – after the war ends – include veterans’ care and restocking weapons’ inventory.

“I am certain we will reach one trillion dollars for the Iran war,” she concluded.