Countries that Don't Use the Metric System 2025

The metric system, formally known as the International System of Units (SI), is an internationally recognized system of measure developed in France during the late 1700s-1800s and later adopted by the world at large. The metric system’s base units are the meter for length, kilogram for mass, second for time, ampere for electrical current, kelvin for temperature, candela for luminous intensity, and mole for amount of a physical substance. These base units can also be used to calculate dozens of derived units, from square meters/metres to ohms, lumens, radians, and farads.

Countries that do not use the metric system

It is often stated that only three countries in the world—the United States, Liberia, and Myanmar—do not use the metric system. However, this belief is incorrect. In truth, every country in the world uses the metric system to some extent. However, a few countries, including not only the United States, Liberia, and Myanmar, but also Canada, and the United Kingdom, have not yet converted 100% to metric. These countries instead use mixed systems in which metric units are either used alongside or replaced by another measurement system (typically the British Imperial system).

The United States and the metric system

Arguably the ultimate example of a blended system, the US uses metric units for measurements including time (seconds), volume of wine and spirits (liters), and lighting (lumens and candelas). It also uses both metric and Imperial units for measurements such as volume of soft drinks (sold in both 12-oz cans and 2-liter bottles), distance (miles, yards, meters, kilometers) and nutritional labels; but stubbornly hangs on to Imperial units for measurements such as gasoline (gallons) and personal measurements of height (feet/inches, never cm) and weight (lbs, never kg).

Despite its current mix of systems, the United States has been pro-metric from the start. The US government legalized the use of the metric system in 1866, and was a founding signatory of the Treaty of the Metre in 1875. Additionally, the legislature passed the Metric Conversion Act in 1975, designating metric as “the preferred system of weights and measures for United States trade and commerce”. Space agency NASA announced in 2007 that it would use metric units on further moon missions.

However, the US government has stopped short of forcing universal metric adoption, which has been resisted by many commercial industries (due to the expense of switching over) and the majority of the American public (due to the American people’s sense of exceptionalism, reluctance to adopt a French-designed system, and general resistance to change). The extremely slow/stalled pace of metric adoption in the US has led some sources to label the US as the only country in the world that is no longer attempting to completely convert to metric. Conversions in Canada and the United Kingdom are also considered stalled by many sources, though both are further along than the US.

Liberia and the metric system

Liberia was founded in the 1820s by the American Colonization Society, an organization that helped black individuals from the post-Civil-War United States and the Caribbean relocate to Africa. As such, many of Liberia’s laws and customs were inspired by the laws and customs of the US. This included its system of measurement, which mirrored the United States customary units (which were themselves largely derived from British Imperial units). However, Liberia currently uses a blended system and is reportedly in the process of fully adopting the metric system, particularly with an eye toward facilitating international trade.

Myanmar and the metric system

A traditionally isolationist country, Myanmar announced in 2013 that it intended to convert to the metric system. Like Liberia, Myanmar chose to adopt the metric system in order to streamline international trade—particularly the export of agricultural products such as rice, beans, and maize in Myanmar’s case. However, progress at the local level appears slow, as the switch seeks to displace centuries of tradition, including the “viss”, a unit of measurement used for most edible products.

Basic functionality of the metric system

The metric system is a decimalized system in which units escalate or deescalate in multiples of ten. Thus, the metric system always requires 10 (or 100, 1,000, etc.) of a given unit to equal one of the next highter unit. For example, while the Imperial measurement system holds that 36 inches equal a yard and 1,760 yards a mile, the metric system states that 100 centimeters equal a meter and 1,000 meters a kilometer.

Greek prefixes are used to indicate increasing multiples of 10: deca (10), hecto (100), kilo (1,000), myria (10,000) and so on. Conversely, Latin prefixes are used for decreasing submultiples (amounts less than 1) and include deci (0.1), centi (0.01), and milli (0.001). These prefixes are applied consistently across all unit types. For example, 1,000 watts is one kilowatt, 1,000 grams is one kilogram, 1,000 meters is one kilometer, etc.

Birth and rise of the metric system

The metric system was born in France after the French Revolution in 1789. The French National Assembly directed the French Academy of Sciences to address and fix the system of French weights and measures, which decided to base the system on a natural physical unit. The Academy decided on the length of 1/10,000,000 (one ten-millionth) of a quadrant of a great circle of the earth. The meter is the result of a six-year survey that eventually yielded a value of 39,37008 inches.

The metric system gained traction rapidly between 1850 and 1900. The French decided to turn the system over to international control, and in 1875, an International Bureau of Weights and Measures met in Paris to sign the Treaty of the Meter. Forty countries, including the United States but excluding Britain, signed the treaty, establishing the International Bureau of Weights and Measures. The metric system met general opposition in every country at the time of its adoption, which has been overcome everywhere except for the United States.

Base Units of the Metric System:

Unit name	Unit symbol	Dimension represented
ampere	A	electric current
candela	cd	brightness of light
kelvin	K	temperature
kilogram	kg	mass
meter/metre	m	length or distance
mole	mol	amount (of substance)
second	s	time

The seven base units of the metric system can be combined in functionally infinite ways to derive additional units as needed. A non-comprehensive table containing just a handful of examples of such units appears below.

Example Derived Units of the Metric System:

Unit name	Unit symbol	Dimension represented
square meter/metre	m²	area
cubic meter/metre	m³	volume
kilogram per cubic meter/metre	kg/m³	density
degrees Celsius	°C	temperature relative to 273.15 K
watt	W	power
pascal	Pa	pressure
newton	N	force
gray	Gy	absorbed dose of ionizing radiation