Welcome to Science Class

At the beginning of each semester I give my new students what I've come to call "the metric lecture". Since we do everything in metric units and many of the freshmen have only a vague knowledge of the topic, I tend to go on a tear. Many years ago I put this all down in an essay for them to peruse (and hopefully, gain a little insight along with some humor). I recently updated it and present it for your own use or amusement.

Thoughts on the Metric and English Systems

Consider the following: The United States of America is the only country of any economic consequence on the planet that still widely uses the English system of measurement. Every other country uses Metric (yes, even over in England they chucked the English/Imperial system). So here is the USA as the last holdout, the last kid on the block, still clinging to its precious feet, inches, pounds, gallons, and so forth. Why is this? After all, it is reasonable to assume that unless the English system is somehow easier to use or more accurate than the Metric system, the USA must be suffering some productivity losses since no other country "speaks the same language". Clearly, manufacturers are going to have a tough time selling English parts in Metric markets. Thus, it is fair to ask:

1. Is the English system more accurate than the Metric system?
2. Is the English system easier to use than the Metric system?
3. If items 1 and 2 are not true, why is the USA still using the English system?

Let's take a look, shall we?

The accuracy of any system of measurement is only as good as its standards and tools. There is no fundamental reason why one system must be more accurate than the other. In practice though, it may well be that the tools offered in one system are superior due to the large number of users (perhaps solely in terms of cost/performance). This would tend to put the English system at a disadvantage these days, but let's be cautious and call this even since we don't have any hard data to verify this hypothesis.

Is the English system easier to use than the Metric system? To hear some people talk, you might think so. For example, in the 1970's when the USA was considering to make a voluntary transition to Metric, grocery items were labeled with metric equivalents. Also, people were inundated with news clips concerning how to convert from one system to the other. "There's 2.2 pounds in each kilogram, Johnny, and a kilometer is about .62 miles." People found this confusing, especially since they didn't really understand all this business about kilo and milli and so forth. All of the measurements seemed to contain parts of the same words. This became particularly nasty when someone would go into a store and see a bag of chips labeled as "454 grams" next to their beloved "1 pound". They must have been thinking "Good Lord, how can this be easier? I can remember 1 pound, but I can't remember 454 grams. It's just dumb." And thus, this author believes, there grew an inherent distaste of the Metric system in the USA (of course, the fact that this is a system developed and used by so-called foreigners may have something to do with it as well).

Let's flip the labels. Imagine you walk into a store and instead of seeing a nice round figure like "1 pound", you see a nice round figure like "500 grams". By doing this, the English equivalent gets all of the ugly trailing digits that no one likes. Neat to be sure, but this is just a cute psychological trick. After all, no one buys items in a grocery store based solely on the amount specified on the label. People buy things by relative size. The average person looks at a bag of pretzels and thinks "This should be enough for the party". They don't calculate that they'll need precisely 22 ounces and then buy a 22 ounce bag. It's for this very reason that manufacturers make "almost round" weights. Where it was once common to buy 1 pound (16 ounce) bags of chips, you can now find 15.5 ounce bags, 14.75 ounce bags and so on. After all, if you reduce the size while keeping the sticker price the same, your profit grows. Most people won't even notice that what they bought isn't quite a pound. To alleviate this problem, the government decided that it would be good to place "unit pricing" stickers on the shelves, indicating the actual cost per pound, per ounce, and so forth. One problem here is that one bag of cookies may give the unit price per ounce while another gives it per pound. The average consumer isn't going to attempt the ounces/pounds conversion in their head.

A case in point is the big bottle of soda. At one time it was normal to buy one or two quart bottles of soda. You couldn't find a two quart bottle of soda if your life depended on it these days. Instead, your local grocery is packed with 2 liter bottles of soda. If you look closely, you'll note that it says "2 liters (67.6 fluid ounces, 2 quarts 3.6 fluid ounces)". Like the guy with the pretzels, people don't have a problem with this conversion since there is no conversion to be made! People think "This looks big enough" and they buy it. That's it. They don't go home and dump 3.6 fluid ounces down the drain because they really wanted 2 quarts. Further, this author has never heard of a case were someone inadvertently bought way too much soda because they screwed up the conversion between quarts and liters. After all, if they mistakenly figured that 3 quarts was about 45 liters, they'd discover their error pretty quickly in the soda aisle. Interestingly, it is worth noting that while Americans are fine with liter soda bottles, they are still forced to buy their dairy products by the quart or gallon.

In short, we've seen that the average American had no trouble replacing their English soda bottles with Metric soda bottles. If they can do this, they should be able to handle any other measurement. "But", you ask, "why would they want to?" The simple answer is (drum roll please...)

Because the Metric system is far easier to use than the English system.

What? What about all of those conversions? Forget the conversions. Remember this: You only need conversions if you plan on using both systems simultaneously. The USA has no reason to use both since it's the only country that still uses the English system. If the USA abandons English units, everyone will speak the common language of Metric units. We won't ever need pounds, feet, miles, gallons, or teaspoons again. No longer will school children (and adults alike) be plagued with questions like "How many feet are there in 2.5 miles?" (remember now, there's 5280 feet in one mile - what a nice round figure.) "If I play a 7200 yard golf course, how many miles did I walk?" (let's see, 3 feet per yard, 5280 feet per mile...) "A recipe calls for 1/4 cup of water for 8 servings. If this is reduced to 3 servings, how many tablespoons of water are required?" If we switch, the only people that will need to care about conversions are historians.

The main problem with the English system is that it has so many names for the same thing. We have something we call weight. If it's on a human scale, we have a unit called pounds. If it's a lot bigger, we have tons. If it's smaller we have ounces. The killer is that we have weird conversions between them. 2000 pounds make one ton, but only 16 ounces make one pound. We've got gallons for liquid measure. Four quarts make one gallon. Two pints make one quart. Two cups make one pint. 16 ounces make one cup (or is it 8? Never mind the fact that we already used the term "ounces" for weight.) What's going on here? How about a little consistency? The English system makes it difficult to combine or split quantities because you have these goofy conversion factors.

In contrast, the Metric system really only has one unit for each item of measurement. If we're talking distance, then we're talking meters (for those of you who positively need the conversion, it's about 10% more than one yard. If you play golf, think meters. It's just like those liter soda bottles.) For bigger distances, we just stick a "kilo" in front which means "1000". (If you're reading this from a computer, you must be familiar with terms like kilobytes and megabytes, right? "Mega" is short for "one million".) If we're talking about small distances, we reduced this to millimeters or even micrometers (milli is 1/1000 and micro is 1/million). The key here is that to translate from big units to small units all we have to do is move a decimal point. To put feet into miles you have to divide feet by 5280. What a pain. To put 2300 meters into kilometers is easy! Just move the decimal 3 places and you've divided by 1000 (2.3 kilometers, or in long hand 2.3 times 1000 meters).

So, for distance (feet, miles, etc.) we'll use meters, for liquid measure (gallons, cups, etc.) we'll use liters, and for weight (pounds, tons, etc.) we'll use grams. (Technically, grams represent mass, not weight. Weight depends on the gravitational field you're in while mass doesn't. If you don't plan on moving to Mars any time soon, don't worry about it.)

Now if you still have doubts about the logic behind this system, just imagine taking a system wherein you already use powers-of-ten and replace it with something entirely inconsistent. Consider US currency. There are dollars and there are cents (100 cents to the dollar, pretty easy). For larger quantities you might use "kilo dollars" as in "that new job starts at $55k". Imagine that instead of the existing system, there were 12 cents to the zarg and 15 zargs made a dollar. Also, 3400 dollars made a fliknek. So, you might read an advert for a job which pays 16.5 flikneks and another for a new car at 9 flikneks, 299 dollars. A big of chips? Maybe 3 dollars, 9 zargs. Does this sound like a logical system, a system you'd prefer over the current system? If not, why not?

If you find the Metric system confusing, make the following changes to your vocabulary. Instead of saying yards, say meters. Instead of saying quarts, say liters. Instead of saying pounds, cut it in two and say kilograms. These approximations are accurate to within 10% and that's good enough for everyday conversation. After a while, this will come naturally, and you'll begin to get a sense of the size of things like kilometers or milliliters. After all, humans are amazingly adaptable, and familiarization will bring this. Indeed, there are many industries and pursuits in which individuals use the Metric system on a daily basis. (Ask any engineer, chemist, or physicist for starters.)

Our third and final question asks why the USA hasn't switched completely to the Metric system. This author doesn't have a good answer. It might have something to do with short-term thinking, greed, stupidity, ignorance, or simple inertia. Just how much does it cost the USA to not go Metric? Well for starters, how about the 125 million dollar Mars Climate Orbiter that took a nose-dive into the surface of the red planet in 1999 because a sub-contractor used English units instead of Metric? At the time, some folks were talking about a failure of a "cross-checking system" to catch these sorts of errors, conveniently ignoring the fact that the money and time spent on such a system would not be needed at all if the USA just went Metric. One newspaper article noted that 95% of the planet currently uses Metric. This factoid is particularly humorous when you realize that that non-Metric 5% is the USA! (The USA currently accounts for approximately 5% of the global population.)

One thing is clear, there's no need for it to stay this way, and there are good reasons to change. Just say no to the English system of measurement. The brain you save may be your own.


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Interesting post! Though I don't see any need for ordinary people to switch units, the mechanical engineering community seriously needs to move from BTUs to Joules. There are many engineering courses at my university where the units are entirely English.

After 15 years in the States, I still have no idea what Fahrenheits mean. Only distance measures are easy enough to get a feel for (mile, yard, foot, hand, inch). Weights are sorta OK, though I have to think. Volume is just plain nasty in English measures and I don't even attempt it any more. Perhaps that is why I only drink Coke - it comes in nice metric bottles of 2L.

Fahrenheit was a guy like Celsius. The Fahrenheit scale is based on the fact that the human body temp should be 100 o. Only he got it a little bit wrong or the got readjusted some how. Wikipedia has some interesting ideas how that came about. Celsius is based on the freezing and boiling temp of water.

I always find it amusing that English pints (16 fl oz)are smaller than Imperial pints (20 fl oz), which is what we older English still use.

Thanks for this post. I've been ranting about the need to convert to metric since back in the '50s.

A few thoughts:
- Besides soft drinks, wine and liquor (but not beer) are now in standard metric containers.
- Running sports (except the marathon) have been using metric distances for years.
- You'd think the petroleum industry would get behind metric conversion. 52.8 cents/liter sounds a lot cheaper than $2.00/gallon.
- Way back, one of the arguments against conversion was that it would cost huge amounts to convert factories producing hardware (nuts, bolts, screws, etc.) and tools to metric, but now that almost all hardware and tools are produced in Asia, we're probably paying a premium to get our hardware in different sizes than the rest of the world.

A final thought. It strikes me that the science blogging community could provide a major service to the US by joining together to push the metric system.

Although I vastly prefer the metric system, I think the reason the US hasn't switched over is failry easy to realize: the short-term cost. Think of what the UK went through when it switched. In the long term, of course, it would pay off, but the short-term headaches, combined with both an instant-gratification mindset and the fact that Americans don't really encounter metric measures unless they travel abroad (which isn't common enough to be a problem), just make it seem not worth it, literally.

Once I took an astronomy class aimed at non-majors. The instructor had previously been a TV weatherman in Texas during the 1960s and 1970s. At some point, the NWS started reporting temperatures in both Celsius and Fahrenheit, and encouraged TV weathermen to do the same. So he did. After the broadcast was over, he was told the station was getting a lot of calls, and asked if he might field some of them. He agreed (as he usually did). He got called all sorts of names - a 'communist', a 'KGB Agent', 'anti-American', and many other things he wouldn't repeat.

Personally, I think we ought to respect the Great Patriotism of those good Texans in those harsher, yet Braver times. After all, the symbol for 'Celsius' is 'C' . Rotate it 90 degrees counterclockwise, and it's a pair of Horns. The Sign of the Devil. Perhaps more damning, it's the first letter in many evil words, such as 'communism', 'comrade', 'cuttlefish', and, of course, 'Celsius'.

America Defeated Communism in part because Great Patriotic Americans like the aforementioned citizens of Texas stood strong against the metric system and the KGB-infiltrated National Weather Service. Today, we face a far greater danger - Terrorists and Radical Environmentalists, who also love the metric system, have infiltrated nearly every major university and research institution.

In addition to being more numerous, Our Enemies are also more devious, particularly in their use of the metric system. In a brilliant feat of reverse psychology, they Brainwashed climate scientists into reporting all findings about Global Warming in metric units. This terrified businesses and conservative groups - and of course they reacted to stop the dastardly plot. Unfortunately, they misunderstood its nature - they assumed Global Warming was a hoax. This is exactly what Terrorists and Environmentalists wanted Businesses and Conservatives to think! The Challenge of Global Warming, like all Challenges, presented American engineering and energy industries with an opportunity to offer highly profitable solutions. But solutions were exactly what Radical Environmentalists did not want. So they tricked businesses and conservative groups into thinking Global Warming was a hoax, squandering our great opportunities. And they accomplished their foul end by use of the metric system.

I remember having in the 1970ies a Ford Pinto with an engine made in Canada (using metric screws etc.) and the rest in the U.S. For any repair, one needed a metric and an English set of tools.--
This problem is still with us, as my workplace has a fair amount of
imported high-tech devices, which, of course, are metric, but the local
shops prefer English units; so I see often enough things designed, in metric, by the lab's engineers and scientists, with then the design transferred to inches and mils for local fabrication.--
The problem is indeed with the short-term cost, no CEO of a major
company wants to depress this quarter's profit by a charge for re- tooling to metric. And since the 1970ies, no president tried to push for it.--
(Click on SI-Units below for info on the 'International System' of units,
courtesy of NIST, the National Institute of Standards and Technology)

A final thought. It strikes me that the science blogging community could provide a major service to the US by joining together to push the metric system.

Sounds like an interesting idea chezjake, but I'm not sure how we might go about it. I think we would wind up "preaching to the choir".

Regarding the big "Why not?", I concur that it has a lot to do with short-term thinking. I also know that the entire building trades industry is against it as all the standards currently use English units. Just think of building a house: studs 16" on center, 4x8 sheets of plywood, electrical routing specified in feet and/or inches, pipes measured in inches, etc. I think most of this can be easily swept away with "soft metric" conversions (like studs .4 meters on center, which is just a shade under 16"), but the construction trades in the US are not known for their embrace of new technologies and methods, and they are pervasive.

"Think of what the UK went through when it switched."
The UK has never truly switched, all of the road signs (even new ones) are in miles, you still buy a pint down the pub, any market stall in the country will sell you 5lbs of potatoes, horse races are measured in furlongs, and for as long as the game of cricket is alive in England (which may not be much longer if we continue to play like we did this morning) the "chain" will be the standard unit of measurement. Jim, you might find this website useful to emphasise the complexity of the Imperial system http://content-usa.cricinfo.com/ci/content/story/89685.html - I'm English, I've played cricket since I was 6, and I don't understand what he's saying! BTW it's not actually the "English" system, except in America, since most of the measures originate from before England existed, some Imperial measures originate from Roman times, while others are Anglo-Saxon.

By hopper3011 (not verified) on 26 Jan 2007 #permalink

Yesterday I submitted a comment that was intended to be humorous. If it wasn't, I appologize. If it just got trapped in the spam trap, I'd appreciate it if someone would fish it out and post it.
thank you.

Thank you for rescuing my comment!

coturnix, as wikipedia points out, the actual dimensions of a 'two by four' are 1¼Ⳡx 3½â³

coturnix, as wikipedia points out, the actual dimensions of a 'two by four' are 1¼&#8243 x 3½&#8243

Sorry for the double post. I had to find out if it was really the preview that ruined my unicode one-half and one-quarter symbols. (And it is the preview ... they work fine if I don't preview.)

I agree on everything *except* for temperature. I find that the fahrenheit scale is much better for the range of temperatures one encounters. Not only that, but the fact that the degrees are about 1/2 the range of the Celcius degreees means that the precision is just fine without using decimals.

Some assorted thoughts:

About pushing the metric system: I have heard somewhere that the only other country officially using English units is Myanmar (aka Burma). When I point this out to Americans, they get all blustered (partly because some don't know there is a country called Myanmar). Might this be a way we could push the US along? To be provocative, whenever using an English unit of measure, one would stick in a phrase like "as it is expressed in Myanmar and other backward dictatorships".

Banerjee: your comment on BTU vs. Joules brings back memories of grad school, when calculating heat transfer. Some data in the reference tables would be in BTU per square foot and hour, while some other piece of data needed would be expressed in SI units like Watt per square meter and something else in kcal. So many opportunities for mistakes! *Shudders*

"If you play golf, think meters." This is not a good reason for changing! The ten-percent difference between yards and meters is enough to miss the green on most approach shots if you assume one yard equals one meter. At least, it's a convenient excuse when over- or undershooting the green, and you wouldn't want to deprive me of that great excuse, would you? (After all, golf is the game of great excuses...)

On temperature, I disagree with KeithB: except when measuring a fever, most people rarely need precision to the level of decimals of degrees Celsius. Just think of a weatherman, who will usually say something like "highs in the low fifties", not "the high temperature will be 53 degrees Fahrenheit".

Let me close with a standard quip on this topic: "The US is going metric - inch by inch..."

Late to the thread, but:

Personally, I think we ought to respect the Great Patriotism of those good Texans in those harsher, yet Braver times. After all, the symbol for 'Celsius' is 'C' . Rotate it 90 degrees counterclockwise, and it's a pair of Horns. The Sign of the Devil.

If you say horns in Texas, they don't think devil horns, they think hook 'em horns. This could actually be a marketing tool.

After all, if you reduce the size while keeping the sticker price the same, your profit grows.

No conspiracy theories needed: they adjust the size to keep the price constant given the fluctuating price of ingredient. Saves repricing the item all the time.

You see it with chocolate bars: the bars get smaller and smaller (with a constant price), then it's "king size" bars on special for the same price, and then they reprice the bars and the cycle begins again.

By Paul Murray (not verified) on 23 Aug 2008 #permalink

why cant we just keep the us customary sytem it is easier and then there wouldnt be arguing