What are the dimensions of subatomic particles?

Depends which particles. First it's important to note that particles are not like billiard balls, they are infact fluctuations in fields or Quanta. This makes discussion of their size and shape much more complex. So rather niavely lets look at few examples. read more

Subatomic particles play two vital roles in the structure of matter. They are both the basic building blocks of the universe and the mortar that binds the blocks. Although the particles that fulfill these different roles are of two distinct types, they do share some common characteristics, foremost of which is size. read more

But we can give sizes which we know these particles must be smaller than, and right now this is about 10^-18 m = 10^-16 cm, as good as we can measure using subatomic particle colliders like the one at CERN. read more

Composite subatomic particles (such as protons or atomic nuclei) are bound states of two or more elementary particles. For example, a proton is made of two up quarks and one down quark, while the atomic nucleus of helium-4 is composed of two protons and two neutrons. read more