On My Honor: Give me an inch and I’ll take a kilometer

by / 0 Comments / 29 View / July 7, 2015

Michael Brown

For several years, I drove a Jeep that was manufactured in Canada. The speedometer was in kilometers, not miles, per hour. It took a bit of effort, but after awhile, I was able to determine equivalents for km/h and mph fairly easily. Working that out in my head seemed to make the miles, er kilometers, go by faster. It made me wonder why we have two systems of measurement anyway.

In 1975, President Gerald Ford signed into law the Metric Conversion Act, which declared the Metric System of weights and measures to be the preferred system for United States trade and commerce. The law directed departments and agencies within the Executive Branch to take appropriate action. Forty years later, U.S. students still have to learn two systems, and adults are often confronted with making pesky conversions in their heads.

In Texas, students in the early grades begin to learn about the “Customary System,” which involves using inch rulers and learning fractions, such as halves, fourths, and eighths. By the end of grade five, students must be able to convert and solve problems involving customary units of length inches/feet/yards, etc. For example, how many 8-ounce cups of fruit punch can be poured from a 2-gallon jug? At the same time, students in every other industrial nation would use the metric system to determine the number of 200-milliliter cups of fruit punch in an eight-liter container. That involves simply dividing 8,000 by 200 to get 40.

The key to the metric system is the use of “base 10” numeration. Ten tenths make one, ten ones make ten, ten tens make one hundred, and so forth. Counting with metric units and performing operations with them is the same as we normally do with money. In the same way as 8,000 pennies is $80, 8,000 milliliters is 8 liters. Interestingly, we can thank Thomas Jefferson and the American Revolution for our base 10 system of money. Adopting a base 10 monetary system allowed us to discard the English system of pence, shillings, crowns, and farthings. Imagine how much more instructional time our students would spend today learning about fractional units of money.

Our decision to keep teaching customary units requires that students, and their teachers, will keep spending a considerable amount of instructional time learning two systems instead of one – the most difficult of which is one virtually no one else in the world uses. It has been shown that teaching the customary system requires one additional year of mathematics instruction per student, which adds an additional $8.5 billion per year to the cost of K-12 education. Today, it is estimated that, overall, the U.S. economy loses over $6 trillion dollars per year by using two systems of measurement. In 1999, the U.S. lost a Mars probe, at a cost of $125 million, because of a conversion error between customary and metric units. The costs associated with changing signs and relabeling packaging seem well worth the reward.

Recently, Democratic presidential candidate Lincoln Chafee suggested we complete the transition to help keep the U.S. economy number one. I like that he is basing his candidacy, in part, on ways to benefit everyone, instead of select interest groups. Some may think his proposal un-American. But I believe the sooner we make the change the better. And I’d like to know what the other candidates think about it.

Michael Brown is an education consultant and former teacher. He can be contacted at