Why (Almost) Every Country Switched to the Metric System—and Who Still Holds Out

March 10, 2025 Alex

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Imagine buying a liter of milk in one country, then traveling to another where milk is sold by the gallon. Confusing? Absolutely. But for much of history, that was normal. The world was a patchwork of different measurement systems, each with its own logic—or lack thereof.

The World Before the Metric System

Before the metric system, countries used a variety of measurement systems, often with little consistency. Among the most notable were:

The Imperial System (UK and former British colonies) – Included inches, feet, yards, miles, pounds, and gallons.
US Customary System – Similar to the imperial system but with some key differences, such as volume measurements.
Various Local Systems – Many countries had their own traditional units, from the Japanese shaku to the Russian verst.

This lack of standardization made international trade, science, and engineering unnecessarily complicated. Something had to change.

The Birth of the Metric System and Its Scientific Basis

The metric system was born out of the French Revolution in 1799. It was designed to be logical, universal, and based on immutable natural phenomena. Key features included:

Base-10 Simplicity – Everything is based on powers of ten, making conversions straightforward.
Tied to Nature – The meter was originally defined as one ten-millionth of the distance from the equator to the North Pole. Later, it was refined based on the speed of light.
Standardized Across Disciplines – Scientists, engineers, and everyday people could all use the same units without confusion.

Why Countries Switched to the Metric System

The benefits of the metric system were too good to ignore:

Easier Trade and Communication – A global standard made commerce smoother.
Simpler Education – Children no longer had to memorize complex conversion factors.
Scientific Progress – Almost all scientific research uses metric, allowing for seamless collaboration.
Better Engineering and Manufacturing – Metric precision improves consistency in design and production.

The Global Shift: Who Switched First and Who Lagged Behind

France led the charge, adopting the metric system officially in 1799. Other European nations followed, often gradually. By the late 19th and early 20th centuries, most of the world had either switched or begun the transition.

Mapped: In what year did countries finally switch to the metric system?

However, a few countries have held out. Notably:

The United States – Despite officially recognizing the metric system in 1866 and making it legal for trade, the U.S. still primarily uses customary units in daily life.
Liberia and Myanmar – These two countries historically resisted but have recently started shifting toward metric.

Why Some Countries Still Use Alternative Systems

If the metric system is so great, why hasn’t everyone switched?

Cultural Inertia – People are used to what they know. Changing signage, education, and manufacturing standards is costly and time-consuming.
Economic Factors – Some industries, particularly in the U.S., would face huge expenses in transitioning to metric.
Public Resistance – Many Americans, for instance, feel no urgency to change, since the current system still works for them.

The Future: Will the Whole World Go Metric?

The trend suggests that even holdout countries are slowly shifting. In the U.S., industries like medicine, science, and global manufacturing already use metric. In everyday life, dual-labeling (e.g., soda sold in liters) is common. Over time, the push for standardization may lead to full adoption, but for now, inches, pounds, and miles persist in a few corners of the world.

Do you think your country should fully adopt the metric system? Share your thoughts in the comments!