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Elizabeth Benham


Busting Myths About the Metric System

Published: Wednesday, November 11, 2020 - 12:01

This year will be the 45th anniversary of the Metric Conversion Act, which was signed on Dec. 23, 1975, by President Gerald R. Ford. Normally, we celebrate by sharing metric education resources, but this year I want to use the occasion to dispel some common misconceptions about the U.S. relationship with the metric system.

You’ve probably heard that the United States, Liberia, and Burma (aka Myanmar) are the only countries that don’t use the metric system (International System of Units or SI). You may have even seen a map that has been incriminatingly illustrated to show how they are out of step with the rest of the world.

Countries that have not "officially" adopted the metric system (The United States, Myanmar, and Liberia) in gray. Credit: AzaToth [Public domain], via Wikimedia Commons


It’s a compelling story and often repeated, but you might be surprised to learn that it’s simply untrue!

While it’s true that metric use is mandatory in some countries and voluntary in others, all countries have recognized and adopted the SI, including the United States.

Russ Rowlett, retired University of North Carolina at Chapel Hill professor of education and mathematics, emphasizes on his website that becoming metric is not a one-time event but a process that happens over time. Every international economy is positioned somewhere along a continuum moving toward increased SI use. There are still countries that are amending their national laws to adopt a mandatory metric policy and others pursuing voluntary metrication.

The United States was one of the original countries to sign the Treaty of the Meter in 1875, which is now celebrated annually on May 20, World Metrology Day. It’s been legal to use the metric system since 1866, and metric became the preferred system of weights and measures for U.S. trade and commerce in 1988.

Metric system use in the United States lies along a continuum where some measures are entirely in metric and others are entirely devoid of it, at least at the consumer level. Credit: E. Benham/NIST


Did you know?
• We use the SI every second of every day. After all, the second (s) is the SI base unit of time.
• U.S. coins and currency are produced using metric specifications.
• Many U.S. products, like wine and distilled spirits, have been successfully sold with only metric measures since the early 1980s.
• Metric units are used extensively on packages to provide net quantity, nutrition, and health-related information, and for prescription drugs, over-the-counter medicine, vitamin supplement dosing, and other consumer products.
• SI units are increasingly used on consumer product labeling in the U.S. lighting sector. Voluntary package labeling standards adopted by flashlight manufacturers help consumers make product comparisons. While shopping, consumers easily evaluate light output (lumen), peak beam intensity (candela), beam distance (meter), and impact resistance (meter).


It’s impossible to avoid using the metric system in the United States. All our measurement units, including U.S. customary units you’re familiar with (feet, pounds, gallons, Fahrenheit, etc.), are defined in terms of the SI—and mass, length, and volume have been defined in metric units since 1893! The SI’s influence is pervasive and felt even if most people don’t know it. I envision the U.S. metric practice like a huge iceberg. Above the water’s surface, U.S. customary units appear to still be in full effect. In actuality, below the water’s surface, we find that all measurements are dependent on the SI, linked through an unbroken chain of traceable measurements.

The U.S. measurement infrastructure depends on the SI. Credit: E. Benham/NIST


Although U.S. customary units are still seen alongside metric units on product labels and merchandise literature, it’s common for the goods themselves to be made using SI-based manufacturing processes. Why? While some businesses are concerned that consumers expect to see customary units on the package, when it comes to manufacturing processes, they are under constant pressure to stay competitive. Adopting the latest science and technology, developed using metric design practices, enables innovation. In addition, many industries extensively use international supply lines to develop, manufacture and sell their products around the world.

I’m the coordinator of NIST’s Metric Program. Because of my passion for all things metric, I encourage companies to investigate adopting metric practices whenever possible and show them how doing so can make a strategic economic impact for their organization. Changes in technology and extremely competitive domestic and global marketplaces can compel businesses with little previous experience to explore metric use. Many have found that going metric pays off, resulting in a competitive advantage.

Going metric pays off

During the recent recession, lumber companies located in the U.S. Northwest saw their U.S. customer base shrink, but their Canadian and Japanese markets, both of which use metric, expand—especially after the 2011 earthquake and tsunami. Wood-product producers made adjustments so that their production systems could flex between metric and U.S. customary measures based on what their customers needed. Because so much of the world uses metric only, more and more U.S. companies are recognizing the benefits of metric as they find new international markets for their products.

If your business is considering making the switch to metric, I would encourage you to conduct small beta tests to explore how your customers react. Research can help ensure decisions aren’t based on out-of-date information or preconceived notions. You might be pleasantly surprised by how quickly customers adapt—and how using metric benefits the bottom line.

And as always, if you need advice, be sure to give NIST a call. We’re here to help!


About The Author

Elizabeth Benham’s picture

Elizabeth Benham

Since becoming metric coordinator at NIST in 2005, Elizabeth Benham has worked to support voluntary conversion to the International System of Units (SI), commonly known as the metric system, in the United States. In addition to providing information and assistance to federal, state, and local weights and measures officials, business, industry, educational institutions, and the public concerning the SI, she also identifies opportunities for increasing its understanding and use in trade and commerce. When she’s not extolling the virtues of the converting to metric, she enjoys hiking with her 60 kg Rottweiler, Matilda.







Adopting to new system

The article gave me better input on the use of Metric system by US companies. One thing I need to mention as an India, India is quick to adopt changes, especialy the measuring system. But, still we keep pace with global world in meeting the requirements mentioned both in the old and new. As mentioned in the article following Metric system has enormous advantage in designing packagings, product enhancements etc. If the metric system is adopted as a global system with sprint conversion by all governments, then growth can be seen swiftly. Hail Metric system.