The metric system is used as the official system of measurement in nearly every country on Earth. Just three countries that don’t use the metric system as their primary standard remain: the United States, Liberia, and Myanmar.
The Three Holdout Countries
- United States — still uses miles, pounds, and Fahrenheit for most everyday purposes, even though the metric system is legally recognized and used throughout science, medicine, and much of manufacturing and international trade
- Liberia — largely uses US customary units, a legacy of its historical ties to the United States
- Myanmar — primarily uses a traditional system of local units alongside some imperial measures, though metric use is gradually increasing, particularly in trade
See area figures — already listed in metric — for these countries on our Rankings page.
Why the US Never Fully Switched
The US Congress made the metric system legal for use as far back as 1866 and even passed the Metric Conversion Act in 1975 encouraging voluntary adoption, but a full switch never happened at the consumer level. The cost of converting existing infrastructure, road signage, and consumer habits, combined with the absence of a strict legal mandate (unlike the UK’s more assertive metrication push), left customary units entrenched in everyday American life even as science, medicine, and the military use metric units extensively.
A Common Misconception: The UK
Many people assume the UK still fully uses imperial units, and it’s true that miles, pints, and stones remain common in everyday British life — but the UK officially adopted the metric system for most legal, scientific, and commercial purposes decades ago, making it a partial, rather than complete, holdout.
Frequently Asked Questions
What countries don’t use the metric system?
The United States, Liberia, and Myanmar are the only three countries that have not officially adopted the metric system as their primary measurement standard.
Does the US use the metric system at all?
Yes — the metric system is legally recognized in the US and is standard in science, medicine, and much of manufacturing and international trade, even though everyday consumer use still relies on customary units like miles and pounds.
Why hasn’t the US fully converted to metric?
The cost and disruption of converting existing infrastructure and consumer habits, combined with the absence of a strict legal mandate, have kept customary units in everyday use despite decades of voluntary metrication efforts.
Compare metric area and population figures for any country with our Compare tool.
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