Expression density (definition) calculation formula: P0 = m/v0P0; Apparent density of material M: mass of material in dry state V0: apparent volume of material Actual density (definition) The volume of actual density does not include pore volume. Calculation formula: P= M/V P: density of substance m: mass of substance in dry state v: bulk density of substance in natural state: bulk volume = particle volume+void volume = particle volume+void volume calculation formula: V=V 1+V2 IV. Density and porosity. 1, compactness: refers to the degree to which the volume of a substance is enriched by a solid substance, that is, the ratio of the dense volume to the apparent volume of a substance. Calculation formula: D= V/ V02. Porosity: the ratio of pore volume to total volume in unit volume. Formula derivation: p = (1-v/v0)) *100% =1-d: d+p =1Further understanding: open porosity.