In chemistry, the molar volume of a substance is the ratio of the volume of a sample of that substance (expressed in litres, for example) to the amount of substance (usually expressed in moles) in the sample. Apart from computing molar volume by dividing the volume of the substance by the amount of substance, it can also be computed as the substance's atomic or molecular mass (whichever is appropriate), divided by its density. The SI unit of molar volume is cubic metres per mole (m3mol-1).