We usually call std cell libs height as 7T, 9T, 12T (tracks). The track herein is metal1 minimum pitch (width+space).
For example,
65nm, metal1 pitch 0.2um (width/space=0.1um/0.1um). 7T cell height is 1.4um (0.2*7).
The Standard Cell Height is derived from metal pitch.
Metal Pitch will be Via to Via , Line to Line (Not used in many libraries) , Line to Via and pSuedo Via .
Also depends on the Application of the Library.
High Density , High Performance or Density or Performance .
When you decide the Height , the DRC rule are referred recursively to place the pins and make the library Porous .