A method of reporting the concentration or "equivalent" weight of an ion or substance in a given volume of water as milli-equivalents per liter. Meq/l is calculated by dividing the mg/l by the equivalent weight of the ion or substance. Reporting the concentration of ions as meq/l is popular by RO chemists for determining whether a water analysis is "balanced" where the sum of the cations equals the sum of the anions.