The Metric System is Born – Decimal Day

On October 1, 1795, France officially adopted the metric system. The law defined the metre (one ten‑millionth of the meridian quadrant) and the gram (the mass of one cubic centimetre of water). Decimal prefixes (kilo, centi, etc.) were introduced. The metric system spread worldwide, becoming the standard for science. Today, only three countries (USA, Liberia, Myanmar) have not fully adopted it. The metric system is an example of mathematical rationalisation of measurement – a dream of the French Revolution that became a global reality.