Units of Concentration – Volume Percent (%v/v)

For liquid chemicals (such as oils and other organic liquids), volume may be more convenient to measure than mass. Percent by volume (or volume percent, vol%, (%v/v), etc) is often used to report concentration for these mixtures:

$$\text{% v/v}=\frac{\text{volume of solute}}{\text{volume of solution}} \times 100\%$$

As with mass percent, remember that the denominator is the volume of the entire solution, not just the solvent (and in many cases, the total volume is not equal to the sum of the two liquids being mixed!)

Calculations using Volume Percentage

Rubbing alcohol (isopropanol) is usually sold as a 70%v/v aqueous solution. If the density of isopropyl alcohol is 0.785 g/mL, how many grams of isopropyl alcohol are present in a 355 mL bottle of rubbing alcohol?


Per the definition of volume percentage, the isopropanol volume is 70% of the total solution volume. Multiplying the isopropanol volume by its density yields the requested mass: $$(355\,mL\;\text{solution})\left(\frac{70\,mL\;\text{isopropyl alcohol}}{100\,mL\;\text{solution}}\right) \left(\frac{0.785\,g\;\text{isopropyl alcohol}}{1\,mL\;\text{isopropyl alcohol}}\right)\\ =\,195\,g\;\text{isopropyl alcohol}$$