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...)
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.