Why Does the US Still Use the Imperial System?
A historical deep-dive into why the United States, Liberia, and Myanmar are the only countries holding out against the Metric system.
The Metric Outliers
Look at a map of the world colored by measurement systems, and you’ll see a massive sea of Metric users. Out of the 195 recognized countries on Earth, exactly three do not officially use the International System of Units (SI), commonly known as the Metric system. Those three countries are Myanmar, Liberia, and the United States of America.
Given that the US is a global superpower heavily involved in international trade, science, and engineering, its refusal to adopt the metric system seems like a baffling logistical nightmare. To understand why the US still clings to inches, pounds, and Fahrenheit, we have to travel back in time.
Pirates, Pirates, Pirates
The story actually begins with pirates. In 1793, the newly formed United States government was actively considering adopting the metric system, which had just been developed in France. Thomas Jefferson, the Secretary of State at the time, was a huge proponent of a decimal-based system.
He requested that a French scientist named Joseph Dombey travel to the United States bringing a copper cylinder (the standard kilogram) and a copper rod (the standard meter). If these artifacts had arrived safely in Philadelphia, the course of American measurement history would have changed forever.
However, Dombey’s ship was blown off course by a storm into the Caribbean Sea. There, the ship was attacked by British-aligned privateers (essentially state-sponsored pirates). Dombey died in captivity, and the standard metric artifacts never made it to Thomas Jefferson. Without the physical standards, the young nation stuck with the British Imperial system they were already familiar with.
The Industrial Revolution and The Cost of Change
By the late 19th and early 20th centuries, the American Industrial Revolution was booming. Huge factories were built, and millions of dollars of heavy machinery were manufactured.
All of this machinery—from the threads on screws to the tracks for trains—was calibrated in inches, feet, and pounds. When the push for metrication gained steam globally, American industrialists lobbied heavily against it. Replacing every tool, mold, and machine in the country would have cost an astronomical amount of money. The economic inertia was simply too strong to overcome.
The Failed 1975 Metric Conversion Act
The United States did actually try to convert to the metric system again. In 1975, President Gerald Ford signed the Metric Conversion Act, which declared the metric system “the preferred system of weights and measures for United States trade and commerce.”
The fatal flaw of the Act, however, was that conversion was entirely voluntary. A Metric Board was established to educate the public, but they had no power to enforce the change.
The public pushback was immense. Drivers didn’t want speed limits in kilometers per hour, weather forecasters were ridiculed for giving temperatures in Celsius, and labor unions argued that forcing mechanics to buy new metric tools was unfair. By 1982, President Ronald Reagan dismantled the Metric Board, effectively ending the government’s push for metrication.
The Hidden Metric Reality
Here is the irony of the American measurement system: The United States is technically a metric country, it just hides it.
Since the Mendenhall Order of 1893, all US customary units are officially defined in terms of metric units. An inch isn’t defined by the size of a king’s thumb; it is legally defined by the US government as exactly 25.4 millimeters. A pound is legally defined as exactly 0.45359237 kilograms.
Furthermore, many crucial American industries are already fully metric:
- The Military and NASA: Use metric to seamlessly coordinate with international allies.
- Medicine and Pharmaceuticals: Dosages are always measured in milligrams (mg) and milliliters (ml).
- Automotive: Most cars manufactured in the US are built with metric components.
- Beverages: While milk is sold by the gallon, soda and water are famously sold in 2-liter bottles.
Conclusion
Will the United States ever fully adopt the metric system? Probably not anytime soon. The cost of replacing every road sign, reprogramming every GPS, and retraining 330 million people makes a sudden switch politically and economically unviable.
Until then, the world will have to rely on fast, accurate converters. If you find yourself needing to translate between these two historical systems, you can instantly convert Miles to Kilometers or Pounds to Kilograms using White Units.