Why doesn't the US use the metric system?

Would you rather use inches or centimeters? (Image credit: Shutterstock)

How people measure stuff might seem pretty bland as topics go, but behind America's insistence to keep drinking coffee in ounces and pumping gas in gallons lies a story with a weighty dose of patriotism, political stability and a historical distrust of the French.

"The paradox is that the way we choose to measure things is banal and boring, but it's also super important because it structures the way we live and interact with each other," said Ken Alder, a professor of history at Northwestern University in Illinois, who wrote "The Measure of All Things: The Seven-Year Odyssey and Hidden Error That Transformed the World (Free Press, 2003). "You can't make comparisons or have an economy without setting standards, and people have bitterly fought for standards because it's really a fight about how the economy works."

In the 1790s, the French Academy of Sciences was asked by the government in Paris to come up with a new and logical system of measurement. The academy decided that the new system should be based on something they could physically quantify in nature, so it could stand the test of time. Thus, they decided a meter should be one 10 millionth of a quadrant of the Earth's circumference — that is, the line running from the North Pole to the equator — a ruling that led to the beginnings of the metric system.

The metric system is arguably an easier way to go about standardizing measurements than the system the United States uses. Everything in the metric system divides into decimals (there are 10 millimeters in a centimeter, 1,000 grams in a kilogram, and so on); most of the rest of the world uses it; and it also just makes sense — for example, water freezes at zero degrees Celsius (as opposed to the random 32 degrees Fahrenheit) and it boils at 100 C (instead of 212 F).

So why hasn't the U.S. budged an inch? Why do Americans continue to use units of yards, miles and pints? The U.S. customary system has morphed and evolved from a hodgepodge of several systems dating back to medieval England. In 1790, George Washington noted the need for some uniformity in currency and measurements. Money was successfully decimalized, but that's as far as it got. In truth, the U.S. did try to make the switch a couple times, but it never quite managed to follow through; the British system was too ingrained in American industry as well as the national psyche.

It even took several efforts by various groups in France before the metric system came to be. It wasn't until the chaos following the 1789 French Revolution that it became possible. "Before then, measures didn't just differ from country to country, but from town to town," Alder told Live Science. In fact, it's thought that prior to the metric system, there were over 250,000 different units of measure in France. Standardizing measures was important to people who traveled. "Local systems screw[ed] over the traders and merchants, whereas the metric system allowed them to know what they were getting. But the locals resisted because they liked what they knew," Alder said.

It's worth pointing out that the old measurements worked well for the French locals because these metrics were tied to physical counting systems. For example, a field's size might be measured by the 'journée' (meaning 'day' in French), which denoted the number of days it took to harvest its crop. Other times, land was measured in 'boisseaux' (or 'bushels'), to quantify how much grain-seed was needed to sow the land. "The old systems did make sense, they weren't just totally crazy," Alder said.

But when the revolution came and Louis XVI succumbed to the guillotine, those who replaced him were part of the Enlightenment movement, during a period known as the Age of Reason, and these new leaders reasoned that Louis' head should be weighed in kilos. "It was the time for rationalization," Alder said. "The United States was supposed to be the second country to adopt the new way of measuring things, as the sister republic."

In 1793, the U.S. Secretary of State, Thomas Jefferson, even sent for a French scientist named Joseph Dombey, who set sail for the New World with a small copper cylinder, which was destined to be America's new standard weight — a kilogram. But Dombey's ship was beset by bad weather; an Atlantic wind pushed Dombey's vessel off course and into the custody of ransom-desiring British pirates. Sadly, he died a prisoner and the kilogram never made it to Jefferson.

But pesky tempests are not the only reason the metric system never caught on stateside; it's also a question of identity, and not all Americans were as Francophillic as Jefferson, Alder said. "I understand when people resent it as a remote force of globalization that produces uniformity, and it's perfectly rational to want local control," he said. "It can also be about taking a position against something that's hyperrational and French."

Even in France it wasn't particularly welcomed. "It literally took 100 years to implement," Alder noted. The controversy hasn't ended there. Nowadays, scientists quibble about the fluctuations of the original kilogram and meter, Live Science previously reported.

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Another factor working against the metric system in the United States is the country's relative political stability; ever since it gained its independence, elections happened instead of coups and revolutions. That didn't do the metric system any favors, Alder said, because to completely overhaul a country's system of measurement requires quite a bit of turmoil for disrupters to take advantage of. "We came close with the Civil War," he said. "But the conflict wasn't sufficiently subversive to make that change."

The United Kingdom for example, only started its journey toward the metric system in the 1970s, after the reality of its geopolitics changed radically; the U.K. not only lost its empire but also began preferentially trading with its continental neighbors over its former colonies, Alder explained. That said, the British have only half-heartedly adopted the new system — road signs are still in miles and pubs still serve beer in pints. (Of note, dry and liquid measurements for pints in the U.K. are not the same as they are in the U.S., according to Encyclopedia Britannica.) Nevertheless, the Jimmy Carter administration tried to follow the Brits around the same time. "[The government] actually tried to put road signs up in kilometers, but people went crazy and it was abandoned," Alder said.

The U.S. Congress even passed a law in 1975 to make the switch, but unlike the United Kingdom, the transition was deemed to be voluntary instead of mandatory and there was no deadline.

So, for those who long for the U.S. to see sense and ditch ounces for grams — be careful what you wish for, Alder said, because more often than not, the transition is accompanied by more drastic political change.

Originally published on Live Science.

Benjamin is a freelance science journalist with nearly a decade of experience, based in Australia. His writing has featured in Live Science, Scientific American, Discover Magazine, Associated Press, USA Today, Wired, Engadget, Chemical & Engineering News, among others. Benjamin has a bachelor's degree in biology from Imperial College, London, and a master's degree in science journalism from New York University along with an advanced certificate in science, health and environmental reporting.

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14 Comments Comment from the forums

garthpool

The book "Measure of All Things" is a great read, well-written and extremely interesting. One of its most valuable revelations is that, despite the general belief, the metric system is not based on a natural and eternal truth.

During the measurements to establish the system, the investigators discovered that the Earth is not a perfect sphere. The length of a fraction of one meridian is different from the length of the same fraction of another. The length of a meter therefore depends on which meridian serves as the basis.

The French realized this toward the end of the project. They were too far into it to make any corrections, if that had even been possible. So they fudged things to establish what we now call the meter.

The metric system is no more rational than any other system. A useful system requires only agreement on which standard to use. The French chose the one they liked, and as the book explains, were able after a good many years to persuade many other nations to use it.

The use of the decimal for the system is vastly overrated. It makes sense for money, but in a physical measurement it is much easier and far more accurate to divide by two by the eye, as the US Customary System allows, than it is by ten. This matters in almost every measurement most of us make. Let the scientists keep their decimals. The carpenter and the cook have a better system.

Granted, it is inconvenient to have two measurement systems in the world, sometimes even deadly. A plane crashed because of it, costing lives. The Mars Orbiter was lost because of it, costing hundreds of millions of dollars and the loss of important opportunities in science.

But it would be extremely difficult for the US to change to the metric system. It would cost an enormous amount of money and aggravation, and it is not necessary. The one we are using is superior in many ways.

Sorry, nerds. You might think you sound superior by using kilometers instead of miles, but you are just following the mindless herd. We should not start calling the inch worm the centimeter worm.
Reply
Hildy

admin said:
Identity, politics and good, old fashioned resistance to change.

Why doesn't the US use the metric system? : Read more
One thing Garthpool and the article alluded to should be emphasized. Much of the Imperial System and none of the Metric System is human centric.

A mile is about a thousand paces (a pace is two steps) and dates to Roman times to measure an army's march and put mile markers on roads.

A yard is about the distance between your nose and your outstretched hand (and I can remember my mother buying fabric measured this way by a fabric shop).

A foot is about a foot (with or without a shoe, depending on your foot size if you want to be more accurate).

An inch was the width of an adult thumb (and children can use an appropriate finger joint).

As far as temperature Daniel Fahrenheit defined zero degrees as the freezing temperature of a brine solution which gave 32 degrees as the freezing point of pure water and 212 degrees as the boiling point. He divided the difference by 180 instead of 100 but it was as scientifically based as Celsius. The benefit that the human body recognizes variations in 1 degree Fahrenheit when setting, say, your heating (just ask my wife) while Celsius requires fractions to get to that point.

I will also point out that the French also created a calendar with a day divided into 10 decimal hours, an hour into 100 decimal minutes, and a minute into 100 decimal seconds. From the metric point of view, this makes far more sense than the current arrangement but it was laughed out of existence after the French Revolution and nobody mentions it anymore.
Reply
Ts60423

This article implies we are not metric. We are. We use both.

The question for decades isn't "why aren't we metric," but instead "why do we use both?"

One could even argue that unless you measure heat in kelvins, you are not metric (Celsius is not metric.)

I have a 100 year old house. It isn't metric. We didn't have to build infrastructure from scratch after WWII, so we have countless legacy systems in place. Interestingly, the US military is 100% metric and has been since at least the 80's. All cars have been metric for decades. I teach both to my students in elementary school. Engineers use metric for design, then convert to imperial units afterwards, if at all. There is no 'going metric' because we did, but our homes (plumbing, lumber, etc.) are not convertible. I really don't notice, though I like my newer tape measures with both units, just to mess with the hardware store or my dad.

The question for decades isn't "why aren't we metric," but instead "why do we use both?" It is a history lesson and a marketing lesson, not a political one.
Reply
mulp

The US is metric. An inch is defined as 2.54cm exactly. The mass unit pound is legally defined as exactly 0.45359237 kilograms.

But then, for some units like pound-force, you must use the definition of slug, which is defined as the mass that is accelerated by 1 ft/s2 when a force of one pound (lbf) is exerted on it. But the slug is defined as 14.59390 kg. Thus pound force is indirectly defined as 143N/14.59390kg, or inexactly as 4.448222 N.

And so on.

SI is the product of physics and it has been modified as needed to conform to what physicists define as "nature".

The customarily used measures in the US are based on how most people think is the way the world works, ie, implicitly a pound is the force you put in a scale, not a mass, with gravity constant and fixed. Thus most measures are flexible, and imprecise. And thus can be given as absolutes. You can say something is a pound while I disagree with both being correct because pound is ambiguous with multiple definitions in customary use. Like Trump.
Reply
twk

The others beat me to it and stole most of my thunder - (also I couldn't get the thumbs up button to work - Sorry garthpool, Hildy, TS60423 and, Mulp).

I've been saying for years that the Imperial System, for everyday use by people, is a Better System than the Metric.
As was stated before, degrees Fahrenheit are more accurate than degrees Celsius. The decade scale use for Metric units is too large a jump for most human, real-world applications. "Give me 0.5 liters of beer" just doesn't have the same ring to it as "Give me a pint!"Centimeters are too small and Decimeters are too big for a lot of human-scale things without a measuring device. "How big was the spider?" - America - "About an inch across" Some metric using country - "About 2.54 cm" ... Really? "How long is it from your elbow to your wrist?" "About a foot" or "About 30 cm, 3 dm, 0.3 meters" the scale jumps too far. I have some friends who visit the USA from France, even when I told him the measurements in Centimeters (doing some carpentry), he had to get out his metric tape measure and measure the distance because it was too hard to envision the distance without a measuring device. I've worked in the electronics field for a good number of years and know the SI units better than the average bear, but other than when talking about very large or very small things Nanometers, pico Farads, etc. Imperial units work much better for me, as do fractions a lot of the time. A pizza might be cut in half then quartered, then eights, with four swipes from the cutter. Next time you get a pizza, try and make a slice 0.125. When I was in school in the 60's and early 70's We learned the metric system - "The wave of the future" that was to make math easier, but it really didn't, I'd rather be 6 foot tall than 182.88 cm.
Reply
Valentine Michael Smith

A convention has utility proportional to the person's mind using it. Like a verbal language, I speak old and new.

@garthpool : I told you money es on da way auht. And so will many tawdry 'hobbies' people have, like building stuff from scratch out of wood. And so on.....
Reply
KMacK

Because a lot of the "Never Metric" types run into trouble when they go past the number three. We ARE a metric nation, and slowly but surely a sensible system of measurement is taking over.
Honestly, a Foot is the length of thirty-six barleycorns laid end to end? A mile is one thousand steps (Maybe if you're a Roman - and the Roman Mile is shorter than the Statute mile). And converting Acres into Square miles and then into Rods...? Make mine METRIC.
Reply
Jim_WY

Ts60423 said:
This article implies we are not metric. We are. We use both.

The question for decades isn't "why aren't we metric," but instead "why do we use both?"

One could even argue that unless you measure heat in kelvins, you are not metric (Celsius is not metric.)

I have a 100 year old house. It isn't metric. We didn't have to build infrastructure from scratch after WWII, so we have countless legacy systems in place. Interestingly, the US military is 100% metric and has been since at least the 80's. All cars have been metric for decades. I teach both to my students in elementary school. Engineers use metric for design, then convert to imperial units afterwards, if at all. There is no 'going metric' because we did, but our homes (plumbing, lumber, etc.) are not convertible. I really don't notice, though I like my newer tape measures with both units, just to mess with the hardware store or my dad.

The question for decades isn't "why aren't we metric," but instead "why do we use both?" It is a history lesson and a marketing lesson, not a political one.

I am an engineer (and millennial) and in the civil/structural world I would say the opposite. The vast majority of my designs and calculations are in U.S. Customary and I hardly, if ever, touch SI metric. twk is on the money. For many things the way the U.S. Customary system is set is better intuitively. I grew up being taught metric mostly in school with some U.S. Customary. Engineering school was funny because the first two years they pushed SI metric, SI metric, SI metric, well then we get into the final two years and grad school and you start seeing more U.S. Customary and then in the actual civil engineering field in the U.S. which is very heavy U.S. Customary. For machining parts and other things yeah SI metric works fine, and in some fields is the more advantaged system. When laying down roads, building dams, buildings, however, I will take U.S. Customary any day of the week.

KMacK said:
Because a lot of the "Never Metric" types run into trouble when they go past the number three. We ARE a metric nation, and slowly but surely a sensible system of measurement is taking over.
Honestly, a Foot is the length of thirty-six barleycorns laid end to end? A mile is one thousand steps (Maybe if you're a Roman - and the Roman Mile is shorter than the Statute mile). And converting Acres into Square miles and then into Rods...? Make mine METRIC.

I am not really a never metric, but I do find attitudes like yours interesting. Does it matter to me what the definition of a yard or meter is? No, not really. You bash those other units of linear measurements but then what is the definition of a meter? The length of the path traveled by light in a vacuum in 1/299,792,458 of a second. Look at that fraction of a second, lets be honest it is just as ridiculous and arbitrary as any other measurement. For the record since 1893 the U.S. Survey foot is defined as 1200/3937 of a meter. Thing is once defined, for the vast amount of human activity what exactly that definition is derived from doesn't matter in the big scope of things. Not like Joe Schmo can accurately measure the speed of light in a vacuum in his garage.

I am glad you brought up land area, because acres is a great practical measurement for land. SI metric on the other hand is very unwieldy for land area. An acre is either 4046 square meters or 0.00405 square kilometers. So if you have a 0.25 or a 5, or a 40 acre lot (typical sizes in practical use) you have respectively either(roughly) a 1010, 20,235, or 161,870 square meter lot or a 0.001, 0.02, or 0.161 square kilometer lot.

I would argue the U.S. went the best route which is take the good of both U.S. Customary and SI Metric and allow us to use the better of the two in certain applications were the other is not as good.
Reply
GeorgeOrwellLives

admin said:
Identity, politics and good, old fashioned resistance to change.

Why doesn't the US use the metric system? : Read more
There really is no compelling reason for the United States to move completely to the Metric system. As said by another poster, we do use both. Second, in the modern realm of technology, there is no inherent advantage to a system with a base1O over the current English measurement system used. And as explained earlier, the English system has more measuring points than Metric. 98.6 degrees, 32 degrees freezing and 212 boiling, 6 feet tall, there are natural and innate to Americans. Again, no compelling reason in the age of technology, where calculation is performed by calculators instead of humans, to change.
Reply
RobG

garthpool said:
The use of the decimal for the system is vastly overrated. It makes sense for money, but in a physical measurement it is much easier and far more accurate to divide by two by the eye, as the US Customary System allows, than it is by ten. This matters in almost every measurement most of us make. Let the scientists keep their decimals. The carpenter and the cook have a better system.

The claim that it's "far more accurate to divide by two by the eye" is not supported and really can't be using imperial measures. Firstly, it's equally as easy to divide by halves using the International System of Units (SI units) as imperial. Half a cup is half a cup whether it's measured in fluid ounces or millilitres.

Using length, 1/4 kilometre is 250 metres whereas 1/4 mile is 1,320 feet or 2.5 chains. I know which of those is easier to work with. How about adding 3/8" and 7/16"? With SI units the division is always of a unit of 10 so the values are consistent, e.g. 1/4 litre is 250 millilitres, 1/4 metre is 250 millimetres, etc. so you just need to learn the decimal equivalents of say 1/2, 1/4 and 1/8 (0.5, 0.25 and 0.125 respectively) and you're got the common halves of SI units of measure.

Secondly, the imperial system is not designed to be easily subdivided by halves anyway. For example, the progression of length units is: 12 inches to a foot, 3 feet to a yard, 22 yards to a chain (which is also 100 links, making a link 0.66 feet or 7.92 inches), 10 chains to a furlong and 8 furlongs to a mile. So 1/2 mile is 2,640 feet, half a chain is 33 feet and half a yard is 1.5 feet or 1' 6". So the "divide by 2" argument just doesn't stack up.

The US uses SI units for electrical measures: volts, watts, ohms, etc. The basic imperial units are all specified in SI units and the US military and scientific communities use SI units. So the precedent is there, it's just that the US is weirdly conservative about certain things to the extent that use of imperial measures is viewed with a kind of religious righteousness and woe betide anyone who tries to change it.
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