How to quantize the shape of a molecule? I am looking for numbers which tell you something about the 3D shape of the molecule, and is also easily calculated.

One of these is the acentricity factor. I am aware of this one. My problem is you calculate acentricit, from thermochemical data, which are usually hard to find, and can contain a great degree of experimental errors. 

A more suitable quantity would be constructed from the groups of the molecule. Is there such a thing? Or what are other quantifiers of molecular shape other than acentricit, factor?
There are lots of descriptors of molecular size and shape that come to mind:


Moments of inertia (e.g., how different are they)
Radii (e.g., enclosing the molecule in a best-fit box)
Surface area or polar surface area (there are existing group-based methods)
Volume (e.g., of the van der Waals surface)


Some people have also used 3D shape descriptors like "spectrophores".