Which countries don't use the metric system?
Three countries remain outside the International System of Units (SI): the United States, Liberia, and Myanmar. Most countries use the metric system as their primary or sole system, but these three continue to rely largely on customary, imperial, or legacy measurement traditions in everyday life and official contexts. Decisions to retain non-metric systems often involve legal frameworks, public education costs, industry standards, and cultural familiarity. This guide explains which countries do not use metric, where hybrid usage occurs, and why change has been slow, drawing on government policy and international standards.
Global adoption of the metric system
The metric system, now the International System of Units (SI), is the official measuring system used by almost every country in the world. Adopted widely after World War II, metric is used for trade, education, science, and government. A handful of countries have not completed full metrication, and a few use multiple systems. The global trend favors metric, but local laws, legacy infrastructure, and practical challenges slow full adoption in some places.
Countries that primarily rely on non-metric systems
Three sovereign states are not officially metric: the United States, Liberia, and Myanmar. In each case, historical, legal, and practical factors explain the continued use of customary, imperial, or pre-metric units. Even in these countries, metric is often present in science, medicine, trade, and some sectors, so daily life can show mixed usage.
United States customary units
U.S. law recognizes metric, but everyday commerce and culture remain largely customary. Road signs use miles and feet, weather reports give Fahrenheit, and consumer goods often label in both systems. Industry compliance exists where economically necessary, but wholesale change has not occurred due to high conversion costs and public familiarity with traditional units.
Liberia's dual usage
Liberia mostly uses customary and US-derived units due to historical ties, though metric is recognized and adopted in many formal sectors, including government and industry. Dual usage means markets, land records, and construction often mix measurements, creating inefficiencies while gradual metric adoption continues in official contexts.
Myanmar's limited metrication
Myanmar has not completed metrication, with markets, road signs, and informal trade still using miles, feet, and local weight measures. Metric is taught in schools and used in some official capacities, but full implementation remains uneven across the country. Reform efforts have been slow, with mixed signals in policy and practice.
Where metric coexists with non-metric units
Metric adoption does not always replace older systems overnight; it can exist alongside them in different sectors. Some countries use metric for roads and fuel but retain imperial for body height and construction. Understanding which unit applies in which context helps interpret labels, maps, legal documents, and consumer information.
Examples of hybrid measurement usage
- United Kingdom: miles and mph on road signs; pints in pubs; metric in most trade and education.
- Canada: road signs in metric, building codes in metric, but older references and some retail in imperial.
- Ireland: metric for most official purposes, yet common references to acres and stones persist informally.
- Australia and New Zealand: fully metric in daily life, with limited legacy references.
Why full metric adoption is challenging
Switching a country’s measurement system requires updates to education, signage, legal documents, tooling, and packaging. Costs can be high, and public familiarity can slow acceptance. Some industries benefit from metric precision, but changing familiar labels may confuse customers. In three countries without official metric systems, legacy infrastructure and cultural habits reinforce traditional units even as global trade pushes toward SI standards.
Factual comparison at a glance
| Country | Official status | Primary everyday system | Notes on usage |
|---|---|---|---|
| United States | Metric recognized, customary dominant | US customary (miles, feet, pounds, Fahrenheit) | Dual use in science, medicine, and some trade; no full metrication |
| Liberia | Metric recognized, mixed usage | Customary and metric | Historical US ties; metric growing in government and industry |
| Myanmar | Metric in education and some sectors | Mixed, with customary in daily life | Road signs and markets often non-metric; ongoing reforms |
Regional and industry-specific metric adoption
In many non-metric countries, specific sectors operate largely metrically. Science, medicine, automotive manufacturing, and international trade often require metric units regardless of national preference. Within countries, cities may feel more metric than rural areas, and younger generations may be more familiar with metric through education and digital devices.
What metrication means for travelers and businesses
Travelers to the United States, Liberia, or Myanmar will encounter a mix of measurement references. Road distances and speed limits are typically in miles and mph, while packaging and some consumer products may show both systems. For businesses, converting data, specifications, and labeling to local preferences reduces friction. Understanding local usage ensures accurate communication in logistics, construction, education, and public services.
Frequently asked questions
- Which countries use only the metric system? The vast majority of countries use the metric system as their official and everyday system, with nearly all United Nations members using metric primarily.
- Is the United States fully metric? No. The U.S. uses customary units widely in daily life, despite metric being legal and used in many professional fields.
- Will Liberia or Myanmar fully adopt metric soon? Both countries recognize metric and some sectors use it, but full adoption faces practical and cultural hurdles, with no firm timeline.
The takeaway
Only three countries do not use the metric system as their official primary system: the United States, Liberia, and Myanmar. Each maintains a mix of practices shaped by history, policy, and cost. Metric is increasingly present in industry, education, and science even where customary units dominate public life. Understanding these differences helps interpret measurements across borders and sectors while recognizing the long-term global trend toward SI units.