Percent pore space can be calculated by using of which formula

Percent pore space is defined by the porosity of a material possessing free space between the mineral grains expressed in percentage. It is proposed by Rebollo et al., 1996.
It depends on the size and sorting of the particles as a cubic or hexagonal package.
$$\% {\text{PS}} = 100 - \left( {\frac{{{{\text{D}}_{\text{b}}}}}{{{{\text{D}}_{\text{p}}}}} \times 100} \right)$$