  At the surfaces of materials, the bulk symmetry of the charge density is
broken and electron spill-out into the vacuum region creates a surface dipole.
Such spill-out has been historically calculated by Lang and Kohn [Phys. Rev. B
\textbf{3}, 1215 (1971)] using average electron density to sucessfully explain
the workfunction in metals. However, despite its initial success, in the fifty
years since it has not been extended beyond simple metals. Here we show that
the degree of charge spill-out is largely controlled by the innate bulk
workfunction $\phi_I$, which is the Fermi level position of $\it bulk$ relative
to the ideal vacuum. By incorporating the contribution of $\phi_I$ to the
surface dipole we show that Lang-Kohn's $\it jellium$ based approach can be
broadly expanded to understand the workfunction over a wide range of metals,
semiconductors, and insulators.
