The countries that have not officially adopted the metric system as their sole or primary system of measurement are generally recognized as Liberia, Myanmar, and the United States. These three nations do not have mandatory metric laws that require the exclusive use of the metric system.
While the metric system, or International System of Units (SI), is the global standard and adopted by nearly all nations, its practical implementation and legal mandate can vary significantly.
Countries Without Mandatory Metric Laws
According to the National Institute of Standards and Technology (NIST), there are three countries where the metric system is not legally mandated for all uses:
- Liberia: Located in West Africa, Liberia primarily uses the U.S. Customary System (USCS) due to its historical ties with the United States. While there have been some governmental efforts towards metrication, it has not been fully implemented, and traditional units remain prevalent in daily life and commerce.
- Myanmar (Burma): Situated in Southeast Asia, Myanmar has historically used its own traditional Burmese units and the imperial system. Although the country officially embarked on a metrication process in 2013, the transition is ongoing, and traditional and imperial units are still widely used in many sectors and by the general public.
- United States: Despite officially recognizing the metric system for scientific, technical, and many industrial applications (including being a signatory to the Metre Convention), the United States Customary System (USCS) is predominantly used in everyday commerce, consumer products, and public discourse across the country.
Nations with Significant Non-Metric Usage in Practice
Beyond those without mandatory metric laws, some countries and regions, while having officially adopted the metric system, still experience significant practical use of non-metric units, often due to strong historical or economic ties to the United States. A research paper completed by Vera (2011) noted that in practice, there were additional regions where non-metric usage was prevalent, particularly referencing areas influenced by the United States and its Compacts of Free Association (COFA). These include:
- Federated States of Micronesia: Although officially metric, its close economic and cultural ties with the United States mean that U.S. Customary Units are widely used in daily life, especially for measurements of length, weight, and volume.
- Marshall Islands: Similar to the Federated States of Micronesia, the Marshall Islands maintain strong links to the U.S., resulting in widespread practical use of non-metric units alongside metric ones in various contexts.
- Palau: As another COFA nation, Palau often relies on U.S. Customary Units alongside metric measurements due to its historical and ongoing relationship with the United States, particularly in areas like fuel sales and packaging.
These examples highlight that while nearly all countries have officially adopted the metric system, the extent of its practical implementation can vary, with non-metric systems persisting in daily life in certain regions, often influenced by historical connections or economic partnerships.
Summary of Countries/Regions with Non-Metric Dominance
The table below summarizes the status of countries and associated regions where the metric system is not the sole or primary system of measurement:
| Country/Region | Legal Status Regarding Metric System | Practical Usage |
|---|---|---|
| Liberia | No mandatory metric laws | Primarily non-metric (U.S. Customary System) |
| Myanmar | No mandatory metric laws | Mixed, but traditional and imperial units still widely used |
| United States | No mandatory metric laws | Predominantly non-metric (U.S. Customary System) in daily life |
| Federated States of Micronesia | Officially metric (de jure) | Significant non-metric (U.S. Customary System) usage (de facto) |
| Marshall Islands | Officially metric (de jure) | Significant non-metric (U.S. Customary System) usage (de facto) |
| Palau | Officially metric (de jure) | Significant non-metric (U.S. Customary System) usage (de facto) |
