Weights, measures, and abbreviations are important to know dose and other details about administration of drugs. The drugs and solutions can be measured by using various units. Metric or decimal system of measure is usually used to measure due to two advantages: its tables are simple as they are based on decimal system of notation and its tables of length, volume and weight are conveniently correlated. A prescription should be written in simple and/or in regional language without using abbreviations however certain abbreviations are still in use as under: time of drug administration, formulations, routes of drug administration, etc. A detailed discussion on the metric system has been also provided in this chapter, which is very helpful for the student or readers.