A look at the global map reveals a truth of how almost every country uses the metric system, yet a few, most notably the United States, continue to rely primarily on the imperial or U.S. customary units.

Liberia and Myanmar are historically grouped with the U.S., though both have made slow, uneven moves toward metrication.

The result is a world where a kilogram means the same thing almost everywhere, but pounds, inches, Fahrenheit, and miles still dominate key sectors of American life.

This divide raises deeper questions about standardisation at a time when global collaboration is no longer optional. Scientists warn that climate reporting suffers when countries use different measurement norms, because conversion errors can alter data quality.

A system that the world mostly agrees on, but not universal

The metric system , created during the French Revolution and later refined by the International Bureau of Weights and Measures (BIPM), is rooted in scientific consistency. It is designed around decimals, making it simple to learn, easy to scale, and globally interoperable.

Today, it is the official system for international trade, scientific research, and nearly all global standards bodies.

However, the United States remains the world’s most influential holdout. According to the National Institute of Standards and Technology (NIST), the U.S. legally recognised the metric system in 1866 and reaffirmed its intention to adopt it with the Metric Conversion Act of 1975, but adoption was voluntary, not mandated.

This single detail is considered one of the main reasons the transition stalled. Industries, retailers, and local governments were never required to change, making the imperial system an enduring cultural and economic habit.

In practice, the U.S. already depends on the metric system more than most people realise. Scientists, the military, medicine, and even many manufacturers work almost entirely in metric. Yet household products, road signage, real estate, and groceries continue to use customary units, creating a split system that’s both familiar and complex.

Liberia and Myanmar are often mentioned alongside the U.S., but their situations differ . Myanmar announced in 2013 that it would begin transitioning to the metric system to streamline trade. Liberia uses metric units in certain industries such as medicine and shipping, but the customary system persists in everyday life.