On May 8, 1790, the French National Constituent Assembly approved Talleyrand's proposal to define a unified system of weights and measures. The preparatory work was entrusted to a commission of the Académie Royale des Sciences in Paris, whose members included famous scientists such as Jean-Charles de Borda, Joseph-Louis Lagrange, Antoine-Laurent Lavoisier, Mathieu Tillet, and Condorcet, joined by Pierre-Simon de Laplace and Gaspard Monge. The unit of length was named the meter. It was defined as the forty-millionth part of the terrestrial meridian, measured by the astronomers Jean-Baptiste-Joseph Delambre and François-André Méchain by means of a triangulation between Dunkerque and Barcelona. The next step was the production of the standard meter, deposited in 1799 at the Conservatoire des Arts et Métiers in Paris.

In 1875, the International Bureau of Weights and Measures was established. It promoted the construction of a new and more precise reference meter consisting of an X-shaped cross-section bar. The new standard was deposited with the Commission in Sèvres, near Paris.

As measurement methods improved, it became apparent that not even this second meter was exactly equal to the forty-millionth part of the terrestrial meridian. To avoid being forced to alter all the benchmark copies of the Sèvres unit, a decision was taken in 1889 to define the meter not as a fraction of the meridian, but as the "length of the standard meter in Sèvres."

Today the meter is defined as the distance traveled by light in a vacuum in a tiny fraction of a second. In conformity with the decimal system, the meter has a series of multiples and sub-multiples.

As also occurred with units of measurement used in antiquity, the word meter—in a number of languages—came to mean both the instrument for measuring lengths and the unit of measurement of those lengths.