What did the US war in Iraq ultimately cost?

America's years-long conflict in Iraq left hundreds of thousands dead, millions displaced and cost trillions of dollars

A convoy of US marines crosses the desert near Diwaniya in central Iraq on April 4, 2003. AFP

The US war in Iraq cost far more than some of the most audacious forecasts in terms of both money and human lives.

Economist Larry Lindsey's $100 billion to $200 billion price tag was dismissed as an overestimate by the administration of president George W Bush, which in 2003 calculated a conflict would be closer to between $50 billion and $60 billion.

And a 2003 analysis from the Brookings Institution that same year estimated the US would face between 100 and 5,000 casualties, compared with up to 100,000 losses for Iraqi military forces and civilians.

But those estimations paled in comparison to the true costs of the war as America's projected 60-day invasion of Iraq turned into a years-long presence in the country and Middle East.

The financial cost of the war in Iraq

The US financial commitment spiralled out of control, far topping pre-invasion estimates as Washington poured more and more troops into Iraq.

By 2006 Congress had already provided the Pentagon with $303 billion to be used for direct-war costs.

In 2007 and with the war reaching its peak, Mr Bush sent another 30,000 troops into Iraq.

The Pentagon's non-base funding — funding provided outside its base budget — also peaked at 28 per cent of the department's budget that year and in 2008, the Congressional Budget Office reported.

A Congressional Research Services Report in 2014 estimated that $815 billion of the $1.6 trillion for military operations were allocated for Iraq.

The CRS also reported that annual war costs decreased from $195 billion at its peak in 2008 to $95 billion in 2014.

It was not until Barack Obama began his term in 2009 that war spending in Iraq trended downwards as US troops began to withdraw from the country.

The wars in Iraq and Syria cost $787 billion, according to a Pentagon 2022 estimate, although it does not include costs such as veteran care, interest paid on debt or other expenses.

Taking into account these costs, the total price of the US war efforts in Iraq is closer to $2 trillion, according to an estimate from Brown University's Cost of War project.

But even after most troops had withdrawn from Iraq in 2011, costs of the war and other US war-related efforts continued to accumulate.

The $2 trillion price tag on US war in Iraq is only a fraction of the total spending for those counter-terrorism efforts. The entire post-9/11 wars cost the US an $8 trillion, Brown University's project estimated.

The figures include funding appropriated for the war, with veteran care alone costing $1 trillion.

Other contributing factors include State Department/USAID operations, Homeland Security spending and interest on incurred debt.

The human cost of the war in Iraq

Again, the true human costs of the war far passed original estimates before the US invasion.

A Pentagon casualty status published on March 14 reported that US military and civilian casualties totalled 4,431, another almost 32,000 military personnel wounded in action.

But that number fails to include the suicide rate experienced by Iraq war veterans and other veterans of America's post-9/11 wars.

But an overwhelming majority of deaths as a direct result of war violence came from civilians.

Although not all civilian deaths were recorded, Cost of War estimates that as many as 209,000 Iraqis were killed in the conflict. Hundreds of thousands were also affected by the war's lingering effects such as water supply and sickness.

Another consequence in Iraq and America's post-9/11 wars was the displacement of millions of citizens. Iraqi civilians accounted for 9.2 million of the 38 million displaced as a result of those wars.

Nearly 1.2 million Iraqis are still displaced, the UN High Commission for Refugees reported.

Ninety per cent of Iraqis have not been able to return home for three years, and 70 per cent have not been able to return for at least five years since they left their country.