  We discuss the sources of uncertainty in calculations of the partial widths
of the Higgs boson within the Standard Model. The uncertainties come from two
sources: the truncation of perturbation theory and the uncertainties in input
parameters. We review the current status of perturbative calculations and note
that these are already reaching the parts-per-mil level of accuracy for the
major decay modes. The main sources of uncertainty will then come from the
parametric dependences on alpha_s, m_b, and m_c. Knowledge of these parameters
is systematically improvable through lattice gauge theory calculations. We
estimate the precision that lattice QCD will achieve in the next decade and the
corresponding precision of the Standard Model predictions for Higgs boson
partial widths.
