  With various sets of the parameters that characterize the equation of state
(EOS) of nuclear matter, we systematically examine the thickness of a neutron
star crust and of the pasta phases contained therein. Then, with respect to the
thickness of the phase of spherical nuclei, the thickness of the cylindrical
phase, and the crust thickness, we successfully derive fitting formulas that
express the ratio of each thickness to the star's radius as a function of the
star's compactness, the incompressibility of symmetric nuclear matter, and the
density dependence of the symmetry energy. In particular, we find that the
thickness of the phase of spherical nuclei has such a strong dependence on the
stellar compactness as the crust thickness, but both of them show a much weaker
dependence on the EOS parameters. Thus, via determination of the compactness,
the thickness of the phase of spherical nuclei as well as the crust thickness
can be constrained reasonably, even if the EOS parameters remain to be
well-determined.
