The void ratio is the ratio of the volume of voids (open spaces, i.e. air and water) in a soil to volume of solids.
e = Void Ratio
Vv = Volume of voids (m3 or ft3)
Vs = Volume of solids (m3 or ft3)
Vg = Volume of air (m3 or ft3)
Vw = Volume of water (m3 or ft3)
The void ratio is thus a ratio which can be greater than 1. It can also be expressed as a fraction.
Void ratio and porosity differ only in the denominator. Void ratio is the ratio of voids to solids, porosity is the ratio of voids to total volume.