How to Calculate Soil Porosity

The soil porosity, also called the void fraction, is the ratio of the volume of voids (open spaces, i.e. air and water) in a soil to the total volume.

n = \frac{V_v}{V_t}\newline\newline    =\frac{V_g + V_w}{V_g + V_w + V_s}
Where:
Vv = Volume of voids (m3 or ft3)
Vt = Total Volume (m3 or ft3)
Vg = Volume of air (m3 or ft3)
Vw = Volume of water (m3 or ft3)
Vs = Volume of solids (m3 or ft3)

Porosity is thus a ratio between 0 and 1, which can also be expressed as a fraction.

It is the fraction of the material that is not solid. The soil porosity is closely related to the void ratio, which is defined as the ratio of voids to solids, rather than total, volume.

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