# Volume percent

### Volume percent

Volume percent is a common expression of a solution's concentration. It is defined as:

$\textrm\left\{volume\ percent\right\} = \frac\left\{\textrm\left\{volume\ of\ solute\right\}\right\}\left\{\textrm\left\{volume\ of\ solution\right\}\right\}*100\%$

Volume percent is usually used when the solution is made by mixing two fluids, such as liquids or gases. However, percentages are only additive for ideal gases.[1]

In the case of a mixture of ethanol and water, which are miscible in all proportions, the designation of solvent and solute is arbitrary. The volume of such a mixture is slightly less than the sum of the volumes of the components. Thus, by the above definition, the term "40% alcohol by volume" refers to a mixture of 40 volume units of ethanol with enough water to make a final volume of 100 units, rather than a mixture of 40 units of ethanol with 60 units of water.