Washington ( CNN ) -- The United States has spent more than $ 1 trillion on wars since the September 11 , 2001 , terror attacks , a recently released Congressional report says . Adjusting for inflation , the outlays for conflicts in Afghanistan , Iraq and elsewhere around the world make the `` war on terrorism '' second only to World War II . The report `` Cost of Major U.S. Wars '' by the Congressional Research Service attempts to compare war costs over a more than 230-year period -- from the American Revolution to the current day -- noting the difficulties associated with such a task . Since the the 9/11 terror attacks , the United States has spent an estimated $ 1.15 trillion . World War II cost $ 4.1 trillion when converted to current dollars , although the tab in the 1940s was $ 296 billion . World War II consumed a massive 36 percent of America 's gross domestic product -- a broad measurement of the country 's economic output . The post-9/11 cost of the conflicts is about 1 percent of GDP . Comparisons of costs of wars over a 230-year period , however , are inherently problematic , the report says . `` One problem is how to separate costs of military operations from costs of forces in peacetime . In recent years , the DOD ( Department of Defense ) has tried to identify the additional 'incremental ' expenses of engaging in military operations , over and above the costs of maintaining standing military forces . '' `` Figures are problematic , as well , because of difficulties in comparing prices from one vastly different era to another , '' according to the report . `` Perhaps a more significant problem is that wars appear more expensive over time as the sophistication and cost of technology advances , both for military and for civilian activities . '' The costs associated with the `` war on terrorism '' could still go much higher . A Congressional Budget Office estimate from 2007 said the cost of the wars in Afghanistan and Iraq could total $ 2.4 trillion by 2017 , more than double the current amount . CNN 's Ed Payne contributed to this story .
`` War on terrorism '' is second most-expensive war in U.S. history , report says . Adjusted for inflation , World War II cost more than $ 4 trillion . The cost of the wars in Afghanistan and Iraq could total $ 2.4 trillion by 2017 .