Giving the inch its due
Metric is great, but there's still a place for some units in the US system
Inch by inch, we’ve crawled our way to Friday. Congratulations. And thanks for being here for another free Friday story. Today - a small defense of the US standard system of measure. Sure, it’s easy to hate and hard to love. But there is a small modicum of value in this much-maligned suite of measures. Read on to learn what this fraction of redemption looks like. ~JRC
Units of measure - they come in all shapes and sizes. While the vast majority of the world uses the metric system, the US does not. Well, not entirely, anyway.
But why not? Why do we Americans continue to use inches and feet (and yards and miles) with all their nuanced conversions? History, of course. And economics too. We've been doing it this way for too long to switch now, as many say. But the arguments for adopting metric are many and varied. And they're good ones.
The rationale for switching to the metric system aside, there's a practical but rarely heard argument why we should still use some of the "US customary units." It's simple too. A few US units are actually useful - and perhaps even better than their metric counterparts.
Heresy, you say? Well, read on, dear reader, to see if this argument stands to measure.
Quickly, the difference.
Most of the world uses the International System of Units (SI), commonly known as the metric system, which is a base-ten method. "Base-ten" means that units up and down the scale differ by, you guessed it, tens. I'm focusing only on length here, so a centimeter is 10 millimeters, for example. A meter is 100 centimeters, and a kilometer is 1000 meters. And so on. It's easy to remember and even easier to use.
Alternatively, the US customary measures system (a.k.a., the US system) uses the inch and its kin for length. There are a host of related systems, often lumped together (e.g., the Imperial system and the SAE - Society of Automotive Engineers system, to name two). Regardless, an inch is 25.4 mm. There are 12 of these in a foot (304.8 mm) and 3 feet in a yard (914.4 mm). The next used length is the mile which equals 1760 yards or 5280 feet (1.61 kilometers or 1,610,000 millimeters). These numbers are difficult to remember and reconcile, to be sure. And it gets more complicated. With the US system lengths - we break down the inch into fractions, not tenths. So an inch is first divided in half, then each half into half again forming quarters, then eighths, and so on. The smallest commonly used is 1/64th which equals 0.3969 mm.
Yes, the US system is confusing, at best. So converting to the metric system makes a lot of sense - intuitive sense. But that doesn't mean it will happen.
I remember as a kid gravitating toward the metric side of the ruler. Even when five, metric was the better side of the stick for me - all those seemingly random divisions on the other half were a pain. And as a young scientist, my love of metric continued. I found it a joy to work with the base-ten system and easily converted and calculated through my research.
But switching to metric as a nation is a different story. That is if that nation is Great Britain or a former British colony in North America.
Almost all other countries took the plunge, beginning way back in the late 1700s (France was the first). Great Britain was one of the last and didn't move over to metric until 1965 - Something like 170 years later. The US did so in 1975 with the Metric Conversion Act, but it was voluntary and hasn’t taken hold. As a result, in America, we still muck around with the old system as do the Brits (although not as extensively - same with Canada). And herein lies the challenge. Early adopters beat the development rush of the Industrial Revolution. So their modern cities are metric from the ground up. But not so for the holdouts. The US and the UK waited too long. And now it's a mess, historically and financially.
This didn’t have to be, however. Thomas Jefferson, among other US "Founding Fathers," considered adopting the metric system in the republic's early days. But it never happened. Sticking with the Imperial system back then helped differentiate the fledgling United States from much of the rest of the world. And keeping the Imperial system allowed the US to hang on to its British roots while carving out a path to independence. A path measured in inches, feet, and miles - not centimeters, meters, and kilometers.
As for cost - the expense of switching now is a [somewhat] valid reason not to change over. We continue to use inches, feet, and miles here in the US because our entire infrastructure is built around it. Whole industries would have to be redone if we switched. Retrofitting existing buildings, bridges, and other structures would also be an ongoing challenge. And all the documents and legislation in place - all would have to be retroactively reconciled with the new measures.
But some - many - argue that cost alone is not reason enough to stay. After all, the rest of the world bit the bullet a long time ago. And the US Metric Association (yes, this is a real organization) argues the cost of switching is exaggerated. Instead, the price of not converting to metric is far greater, so the reasoning goes. All the conversions, the duplication of documents, endless adapters, parallel product lines, and of course, the ever-present miscommunication - all these and more add up to a lot of trouble. Indeed, staying with the old system is in many ways digging our own six-foot-deep grave (or 1.83 meters down, depending on who's doing the digging).
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Despite all this argument for and against the US system, it's rare that we ever hear anything about how good it is. Instead, the assumption is "metric is better." And if metric is, in fact, better, then the only reason not to switch is all that fuss about history, money, and stubborn revolutionaries.
But there are a few convenient reasons to continue using some if not all of the US system. At least with feet and inches, there is value.
First, the foot is a useful length that has no equal in the metric world. At 304.8 mm, it's much larger than a centimeter and still larger than the rarely used decimeter (10 cm). Knowing a foot, one can estimate typical lengths like the size of a room. Sure, you can do this in meters too, but a foot fills a sweet spot between small and large measures that makes it rather handy (yes, a foot is handy).
This handy size also equates to the foot's smaller partner, the inch. At 25.4 mm, an inch is two and a half times bigger than a centimeter. It takes fewer inch units to measure something than centimeters units - and way fewer than millimeters. Why does this matter? Well, first try guessing the length of something in inches - say a desk width. Perhaps it's about 21-23 inches. In centimeters, that same guess would be 53-58 cm. But who says that? With inches, it feels intuitive to use odd numbers because one can, by eye, see the difference inch by inch. Even with relatively long lengths. But with the centimeter, one unit is much smaller, so seeing this difference at bigger sizes is harder. Instead, we'd guess more like 50-60 cm (rounding down and up), thereby reducing the overall precision of the guess.
Okay, maybe this argument is a stretch. After all, it's about guessing and not the empirical usefulness of the US vs. metric system. But stick with me for the best reason for keeping the inch - it's about minutia that matter.
The real reason the inch is so helpful is in its fractional units. Yes, those pesky partitions by halves have a place. Compared to the centimeter, the inch is far more divisible. Look at the standard 12" US ruler to see why.
A US ruler has both US inches and metric centimeters on it - both because the US is slowly shifting over to metric after the aforementioned Metric Conversion Act of 1975. Anyway, the centimeter breaks down into 10 millimeters. But trying to divide these in half again is difficult.
Adding lines for "half millimeters" and smaller units is unfeasible on standard rulers and tapes. The lines are too wide to do so. But with an inch, it breaks down easily into 32nds that can be differentiated on common measuring devices. Most important here, 1/32nd of an inch is smaller than a millimeter (1/32" is 0.79 mm, to be exact). What this means is you can make more precise measurements in inches than you can in millimeters. At least with a regular ruler.
Of course, rulers and even tapes are pretty crude measuring tools compared to calipers and other precision devices. And while inches are also measured in decimal equivalents (e.g., thousandths of an inch or "mils"), millimeters can be divided this way too. But for either, you need special tools to do it. And in the day-to-day, real-world application of measure, we survey our lives with tapes and sticks, not dials and calipers.
Yes, for everyday tasks, the inch is the measure with the most. Well, it has the most functional divisions, anyway. And for this reason - and this reason alone - I'll keep with the US system - for now.
So there you have it, a long diversion into a lengthy “why” on why we still use inches here in the US. Arguably, they still have a place - a tenuous one, but an argument for them, nonetheless.
But what do you think? Does my case for the inch measure up? Or does ease-of-use and all the other irrefutable advantages of metric do the US system in? Should the inch be killed off with the whole lot of non-metric measures? Let me know in the comments.
Until next time, keep calm and measure on.
JRC
I hope you enjoyed this story. Want to watch one of my videos on a similar subject? Check out this YouTube video on measuring (and get a link to a free tool by watching - no strings attached):