In addition to molarity, a number of other solution concentration units are used in various applications. Percentage concentrations based on the solution components’ masses, volumes, or both are useful for expressing relatively high concentrations, whereas lower concentrations are conveniently expressed using ppm or ppb units. These units are popular in environmental, medical, and other fields where mole-based units such as molarity are not as commonly used.

### Key Equations

Percent by mass = [latex] \frac{\text{mass of solute}}{\text{mass of solution}} [/latex] × 100 |

ppm = [latex] \frac{\text{mass solute}}{\text{mass solution}} × 10^6 [/latex] ppm |

ppb = [latex] \frac{\text{mass solute}}{\text{mass solution}} × 10^9 [/latex] ppb |

### Glossary

mass percentage (%w/w)

ratio of solute-to-solution mass expressed as a percentage

mass-volume percent

ratio of solute mass to solution volume, expressed as a percentage

parts per billion (ppb)

ratio of solute-to-solution mass multiplied by 10^{9}

parts per million (ppm)

ratio of solute-to-solution mass multiplied by 10^{6}

volume percentage

ratio of solute-to-solution volume expressed as a percentage