Countries That Don't Use the Metric System: The Full List

Only three countries in the world have not officially adopted the metric system as their primary system of measurement: the United States, Liberia, and Myanmar. Every other country uses the metric system, also known as the International System of Units (SI), for everyday measurement.

Introduction

The metric system, developed in France in the 1790s and refined into the modern International System of Units (SI), is the global standard for measurement. It is built on simple, decimal-based units such as the meter, kilogram, and liter, which makes conversion between scales straightforward. Almost every nation on Earth has adopted it for trade, science, and daily life.

Yet three countries stand apart as official holdouts. Understanding their situation requires nuance, because none of them rejects metric units entirely. Rather, they have not made metric the sole official system, and in practice they use a mix. This guide explains each of the three and the systems they use instead.

The Three Non-Metric Countries

• United States: The US primarily uses the US customary system, with units such as feet, miles, pounds, and gallons for everyday life. However, the metric system is standard in science, medicine, the military, and many industries, and it is legally recognized. The US has never mandated a full switch for public use.
• Liberia: Founded in the 19th century with close ties to the United States, Liberia has traditionally used US customary and older imperial units. In recent years the government has moved toward metric adoption, so the country is best described as transitioning.
• Myanmar: Myanmar has long used its own traditional units of measurement, such as the viss for weight, alongside imperial units. Since the 2010s the government has announced plans to adopt the metric system, and the transition is ongoing.

The important nuance is that "not using the metric system" does not mean these countries ignore it. All three encounter metric units regularly, especially in international trade, science, and medicine. What sets them apart is that they have not formally made SI the single official system for all measurement, unlike the roughly 190 other countries that have.

The Imperial and US Customary Systems Explained

The systems used in place of, or alongside, the metric standard descend from older English units. The British imperial system was formally defined in 1824 and includes units like the imperial gallon and stone. The US customary system evolved separately from earlier English units and differs from imperial in some measures. For example, a US gallon is about 3.79 liters, while an imperial gallon is about 4.55 liters.

Both systems rely on units such as inches, feet, yards, and miles for length, and ounces and pounds for weight. Unlike the tidy decimal steps of the metric system, they use irregular conversions: 12 inches to a foot, 3 feet to a yard, and 1,760 yards to a mile. This complexity is a major reason the rest of the world standardized on metric, which converts by simple powers of ten.

Why the United States Never Fully Switched

The United States has flirted with metrication several times. The Metric Conversion Act of 1975 declared metric the preferred system and encouraged voluntary adoption, but it lacked a mandate and a deadline. Public familiarity with customary units, the cost of converting signage, tools, and manufacturing, and general inertia all slowed the change. As a result, Americans still buy milk in gallons and measure road distances in miles, even as scientists, doctors, and soldiers work in metric daily.

Liberia and Myanmar, by contrast, are smaller economies actively moving toward metric, which means the group of true holdouts may shrink over time. Even so, the United States, with its enormous economy and entrenched customary units, is likely to remain a partial exception for the foreseeable future.

Questions and Answers

How many countries do not use the metric system?

Only three countries have not officially adopted the metric system as their primary standard: the United States, Liberia, and Myanmar. Every other country in the world uses the metric system, or SI, for official measurement.

Does the United States use the metric system at all?

Yes. While Americans use US customary units like miles and pounds in daily life, the metric system is standard in US science, medicine, the military, and many industries, and it is legally recognized. The US simply never mandated a full public switch.

Are Liberia and Myanmar switching to metric?

Both are gradually transitioning. Myanmar announced plans in the 2010s to adopt the metric system, and Liberia has moved toward it in recent years. This means the number of true non-metric holdouts may eventually shrink, leaving the United States as the main exception.