  Dust grains influence many aspects of star formation, including planet
formation, opacities for radiative transfer, chemistry, and the magnetic field
via Ohmic, Hall, and ambipolar diffusion. The size distribution of the dust
grains is the primary characteristic influencing all these aspects. Grain size
increases by coagulation throughout the star formation process. We describe
here numerical simulations of protostellar collapse using methods described in
earlier papers of this series. We compute the evolution of the grain size
distribution from coagulation and the non-ideal magnetohydrodynamics effects
self-consistently and at low numerical cost. We find that the coagulation
efficiency is mostly affected by the time spent in high-density regions.
Starting from sub-micron radii, grain sizes reach more than 100 {\mu}m in an
inner protoplanetary disk that is only 1000 years old. We also show that the
growth of grains significantly affects the resistivities, and indirectly the
dynamics and angular momentum of the disk.
