The metric system was developed in France during the late 18th century, with its first practical form completed in 1799 and officially adopted in 1795 during the French Revolution.

Core timeline

  • In the 1670s, thinkers like Gabriel Mouton and John Wilkins proposed early decimal, nature-based measurement schemes that inspired the later metric system.
  • In 1790, the French National Assembly tasked the French Academy of Sciences with creating a new, universal, decimal system of weights and measures.
  • The French government legally adopted the new metric system in 1795, making it the official national system.
  • The first fully realised, practical metric standards (the metre and kilogram prototypes) were completed and deposited in 1799, marking the system’s initial full implementation.

What “developed” really means

When asking “when was the metric system developed,” most historians point to the 1790s, because that is when:

  • The base units (metre for length and kilogram for mass) were defined using properties of Earth and water, instead of arbitrary objects.
  • The system was made decimal, so every unit scaled by powers of ten, which is the defining feature of the metric system.

In other words, while the ideas started in the 17th century, the metric system as a usable, official system was developed and put in place in France between 1790 and 1799, and then spread gradually around the world during the 19th century.

TL;DR: The modern metric system was conceptually designed in the early 1790s, officially adopted in 1795, and practically completed with standard metre and kilogram prototypes in 1799.

Information gathered from public forums or data available on the internet and portrayed here.