Definition:Density (Physics)

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Density is a physical quantity.

The density of a body is its mass per unit volume.

For a homogeneous body it is found by finding its total mass and dividing it by its total volume:

$\rho = \dfrac m V$


$m$ is the body's mass
$V$ is the body's volume

However, if the substance of the body varies throughout, then its density may be a function of position within the body.


The usual symbol used to denote density of a body is $\rho$ (Greek letter rho).

Some sources use $d$, but that has so many other uses that it may become confused with other things.


The dimension of density is $\mathsf {M L}^{-3}$: mass per unit volume.



$1 \, \mathrm g \, \mathrm {cm}^{-3} = 1000 \, \mathrm {kg} \, \mathrm m^{-3}$

Area Density

The area density of a two-dimensional body is its mass per unit area.

Linear Density

The linear density of a one-dimensional body is its mass per unit length.

Also see