Vietnam war cost as percentage of GDP?

Answer 1

The Vietnam War from 1963 to 1973 averaged $750 million to $1 billion/year.

In 1963, The unadjusted GNP was $611.2 billion.

In October of 1969, it crossed $1,000 billion mark

In 1973, the GDP was $1,400 billion

Averaging these numbers over the period comes to just under $1,000 billion/year

Averaging the cost of the Vietnam war comes to just under $900 million/year

So, in the 10 years of the official war, Vietnam cost 0.09% of the US GDP, roughly 1 tenth of 1 percent.