Bench top design, helium gas expansion porosimeter to be used with matrix cup for samples 1″ in or 1½” diameter and up to 3″ in length. Can also be configured for whole core matrix cup style core holders. Utilizes a highly accurate 0-200 psi transducer with linearity and hysteresis of less than ± 0.11 percent of full scale. System can be used in a grain volume or pore volume measurement mode dependent on configuration of core holder(s) used.