The molar volume of a gas is the volume that one mole of any gas will occupy.

1 mole of gas, at room temperature and pressure (rtp), will always occupy 24 dm^{3} or 24,000 cm^{3}.

Note: 1 dm^{3} = 1000 cm^{3}

The following formulae allows for the interconversion between a volume in dm^{3} or cm^{3} and a number of moles for a given gas:

or

__Example 1__:

Calculate the amount, in moles, of 12 dm^{3} of carbon dioxide (CO_{2}).

__Example 2__:

Calculate the volume at rtp in cubic centimetres (cm^{3}), of 3 mol of oxygen, (O_{2}).