Specific volume ($v$) is the volume occupied by a unit of mass of a material. It is equal to the inverse of density. Specific volume may be expressed in $frac\{m^3\}\{kg\}$, $frac\{ft^3\}\{lbm\}$ or $frac\{mL\}\{g\}$ .

$v\; =\; frac\{V\}\{m\}\; =\; frac\{1\}\{rho\}$

where, $V$ is the volume, $m$ is the mass and $rho$ is the density of the material.

For an ideal gas,

$v\; =\; frac\{R\; T\}\{P\; M\}$

where, $R$ is the specific gas constant, $M$ is the molar mass, $T$ is the temperature and $P$ is the pressure of the gas.

Specific volume may also refer to molar volume.