Abstract: The field of the invention relates generally to filling containers with liquid. More specifically, the invention relates to the real-time assessment of the volume filled into containers, particularly in the manufacture of medicaments such as pharmaceuticals. The invention finds specific use in the final stage of drug manufacturing known as fill/finish wherein the drug substance or active pharmaceutical intermediate is prepared as a final drug product in a formulation suitable for administration to patients in need of the same, which is then provided to patients. More particularly, the invention relates to controlling the volume in container via in-line non-destructive monitoring of the fill process.