Volume fraction

In chemistry, the volume fraction $\phi_i$ is defined as the volume of a constituent $V_i$ divided by the volume of all constituents of the mixture $V$ prior to mixing:

$\phi_i = \frac {V_i}{V}$

The SI-unit is m³/m³.

Volume fraction is also called volume concentration in ideal solutions where the volumes of the constituents are additive (their sum equals the volume of the mixtures).

The sum of all volume fractions of a mixture is equal to 1:

$\sum_{i=1}^{N} V_i = V ; \sum_{i=1}^{N} \phi_i = 1$

See also

• For non-ideal mixtures, see Partial molar volume.
• For alcoholic beverages, see alcohol by volume and Volume percent.