It's around 16% of the total federal budget. To be fair about 1/3 of "military spending" is actually Salaries, Medical, Housing and GI/Retirement costs.

It's also the case that none of the CIA, NSA or DHS budgets show up under the military, even though they're performing some of the same functions that would be handled by militaries in other countries.

We also have "black appropriations." So the total of the spending on surveillance and kinetic operations is often unknowable. Add to this the fact the Pentagon has never successfully performed an audit and I think people are right to be suspicious of the topline "fraction of GDP" number.

I think the number is probably much higher than we think - there is probably a ton of not so obvious spending on research and development.

Just want to point out that the NSA is part of the DoD. (Or DoW now)