A method for determining the volume of core samples disposed within a sealed pressure vessel, the sealed pressure vessel containing a prefill fluid having a density, the method including determining the internal volume of the pressure vessel; determining the density of the prefill fluid; determining, using at least one of one or more computers, the net density of the core samples disposed within the sealed pressure vessel; determining, using at least one of the one or more computers, the density of one or more earth strata proximate the respective in situ locations of the core samples; and calculating, using at least one of the one or more computers, the volume of the core samples disposed within the sealed pressure vessel. In an exemplary embodiment, the core samples are sealed within the pressure vessel when the pressure vessel is disposed within an oil or gas wellbore.