Mercury porosimetry is used to measure the porosity of a material by applying controlled pressure to a sample immersed in mercury. External pressure is required for mercury to penetrate into the pores of a material due to high contact angle of mercury. The amount of pressure required to intrude into the pores is inversely proportional to the size of the pores. The larger the pore the smaller the pressure needed to penetrate into the pore. The mercury porosimeter generates volume and pore size distributions from the pressure versus intrusion data generated by the instrument using the Washburn equation.