The metric system is a decimalized system of measurement. Designed during the French Revolution of the 1790s, the metric system brought order out of the conflicting and confusing traditional systems of weights and measures that were being used in Europe at the time. Prior to the introduction of the metric system, it was common for units of length, land area, and weight to vary, not just from one country to another but from one region to another within the same country. As the modern nations gradually developed from smaller kingdoms and principalities, confusion multiplied. Length, for example, could be measured in feet, inches, miles, spans, cubits, hands, furlongs, palms, rods, chains, and leagues. Merchants, scientists, and educated people throughout Europe realized that a uniform system was needed, and in 1790 the French National Assembly commissioned the Academy of Science to design a simple decimal-based system of units.
The three most common base units in the metric system are the meter, gram, and liter. The meter is a unit of length equal to 3.28 feet; the gram is a unit of mass equal to approximately 0.0022 pounds (about the mass of a paper clip); and the liter is a unit of volume equal to 1.05 quarts. Temperature is expressed in degrees Celsius; 0 degrees Celsius equals 32 degrees Fahrenheit.