How much of the matter in the universe is comprised of atoms?

According to NASA, about 4.6% of the total mass in the universe is composed of atoms.

I'm not 100% certain that I believe that's literally true; I think it's an oversimplification and that when they say "atoms" they really mean "normal matter" including neutrinos and the like.

Still, it's the best answer I could find. We still don't know what the masses of neutrinos are, we just know that they're too small to measure and that they can't be precisely zero.