Outline of the metric system

The following outline is provided as an overview of and topical guide to the metric system: Metric system – various loosely related systems of measurement that trace their origin to the decimal system of measurement introduced in France during the French Revolution.

Four variants of the metric system that predate the introduction of SI (1960) are described in varying levels of detail: Between 1812 and 1839 France used a quasi-metric system: Prior to 1875 the metric system was controlled by the French Government.

In that year, seventeen nations signed the Metre Convention and the management and administration of the system passed into international control.

Both the European Union and the International Organization for Standardization have issued directives/recommendations to harmonise the use of units of measure.

These documents endorse the use of SI for most purposes.

"The metric system is for all people for all time." (Condorcet 1791) Four objects used in making measurements in everyday situations that have metric calibrations are shown: a tape measure calibrated in centimetres , a thermometer calibrated in degrees Celsius , a kilogram mass , and an electrical multimeter which measures volts , amps and ohms .
Countries using the metric , imperial and US customary systems as of 2019.