How much space do subatomic particles occupy?

“Occupy” may not be an accurate term. Particles are bundles of information. In some schools of thought (eg Plato's), information is eternal and unbounded by space. In the model used by quantum physics, which has been tested extensively, the information held by particles is in time and space, but broadly. read more

Subatomic particles are points, and as such do not “occupy” space, however they do each have a sphere of influence in space. Cheers. read more

Intergallactic space is much more sparse. Maybe 1-5 hydrogen atoms in any given cubic meter. There is some denser regions of very hot gas maybe 10 to 100 times as dense as the average density of the universe which is about 5 atoms per meter or so. read more

But you'll probably agree that, if it's possible to make any sensible definition of"occupying space" for a subatomic particle, it should involve preventing other things from also occupying that same space. Photons don't do that. read more