High Quality Content by WIKIPEDIA articles! Informally, a physical quantity is a physical property that can be quantified. This means it can be measured and/or calculated and expressed in numbers. For example, "length" is a physical quantity that can be expressed by stating a number of some basic measurement unit such as metres or inches, while "beauty" is a property that is difficult to describe with a number. Formally, the International Vocabulary of Metrology', 3rd edition (VIM) defines quantity as: property of a phenomenon, body, or substance, where the property has a magnitude that can be expressed as a number and a reference Hence the value of a physical quantity Q is expressed as the product of a numerical value {Q} and a unit of measurement [Q].