In chemistry and biology, the dilution ratio and dilution factor are two related (but slightly different) expressions of the change in concentration of a liquid substance when mixing it with another liquid substance.
They are often used for simple dilutions, one in which a unit volume of a liquid material of interest is combined with an appropriate volume of a solvent liquid to achieve the desired concentration.
The following formulas can be used to calculate the volumes of solute (Vsolute) and solvent (Vsolvent) to be used:[1]
In other areas of science such as pharmacy, and in non-scientific usage, a dilution is normally given as a plain ratio of solvent to solute.
For large factors, this confusion makes only a minor difference, but in precise work it can be important to make clear whether dilution ratio or dilution factor is intended.