Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. The porosity can be expressed either as a fraction or as a percentage.
Formula:
ø = VV ÷ VT
WhereVV is the volume of void-space (such as fluids)
VT is the total or bulk volume of material
ø is the Porosity or void fraction