I have previously written about the metric system, describing how this country is one of the few nations that have not adopted its means of measurement.

The United States, together with Myanmar (Burma) and Liberia, still use the Imperial system which includes ounces, inches, feet, miles, gallons and Fahrenheit. Most of them traced back to the length of body parts or everyday items.  

Unfortunately, these units are not easily divisible in parts of hundreds and thousands like the more user-friendly metric system.  Because the metric system is based on units of 10, a measurement given in one unit can be converted to another by simply moving the decimal point to the left or right:  1000 grams equal one kilogram, 1000 millimeters equals one liter, and 1000 meters equals one kilometer. In comparison, U.S. customary units are unrelated.  

A pound has 16 ounces, a quart has 4 cups, a pint has two, a mile has 1,760 yards or 5,280 feet, and similar names sometimes represent dissimilar values.

Fortunately, all three countries do use elements of the metric system and the United States is inching every closer to its adoption. It would be interesting to first look at history and our reluctance.

History

Much of the world adopted the metric system years ago, thanks to France. The metric system was developed in the 1790s during the French Revolution, the idea addressed the inconsistent and incompatible traditional systems of weights and measures which varied across countries or even across a single country’s regions.  

It was the radical nature of the revolution that allowed the metric system to gain traction. After defining the conditions of the metric system, control was turned over to an international body, and by 1875, most industrialized nations agreed to the Treaty of the metre, which founded the International Bureau of Weights and Measures that led to the metric system we know of today.  

The base units of the International System include meter for length, kilogram for mass, second for time, ampere for electrical current, Kelvin for temperature, mole for amount of substance and candela for luminous intensity.  The National Institutes of Standards and Technology (NIST), part of the United States Department of Commerce, publishes the English language version translation of Le Systeme International d’Unites.

Reluctance

Many factors played a role in frustrating the adoption of the metric system in the United States,  but much of the opposition from the 1870s onward came from the manufacturers of high end machine tools.  They based their entire system — which encompassed everything from lathes to devices for cutting screw threads on the inch.  Retooling, they argued, was prohibitively expensive and they successfully blocked the adoption of the metric system in Congress on a number of occasions in the late 19th and 20th centuries.  

In some respects, using the inch made sense:  it could be divided in ways comprehensible to machinists.  

It was built around “2s” rather than “10s,” with each inch subdivided in half and in half again and so forth. This permitted various sizes of screw threads to have some logical correspondence to all the other increments. In fairness, we now have a hybrid system, most American rulers show inches along one side and centimeters along the other. (One inch equals 2.54 centimeters.)  

According to John Marciano in his book, “Whatever Happened to the Metric System?,” the United States was an original signatory party to the 1875 Treaty of the metre, which established the General Conference of Weights and Measures, the International Committee of Weights and Measures and the International Bureau of Weights and Measures.  Even earlier, the Act of July 28, 1866, authorized the use of metric measurement standards in the United States.  

Subsequent to those earlier efforts, there was passage of the 1975 Metric Conversion Act meant to guide America through the process of abandoning its customary measures for metric ones.   

The idea was to make metric the preferred system of weights and measures but the plan  never caught on.   

Recent Changes

As mentioned earlier, there are signs of adoption.  For example, medicines here are dosed in milligrams, beverages are bottled in liters, so are automobile engines.  Athletes run 5-kilometer (K) races. These changes have augmented the U.S. customary system of measurements but haven’t full replaced it.   Weight is still measured in pounds, height in feet, distance in miles, property in acres and recipe ingredients in spoons and cups.

Final Thoughts

There are signs that metric adoption in the United States will continue. Three areas are examples. Electric cars consume energy measured in watts; hydrogen vehicles will use fuel measured in kilograms; and cannabis, which is often sold in grams. According to a recent article in the Wall Street Journal, it may take seven or more generations for the U.S. to be entirely converted.  Our system is still alive and kicking.

Max Sherman is a medical writer and pharmacist retired from the medical device industry.  His new book “Science Snippets” is available from Amazon and other book sellers. It contains a number of previously published columns.  He can be reached by email at  maxsherman339@gmail.com.