Why I don’t like the metric system

For the benefit of Canadians, Jacobins, progressives, engineers, and stuck-up stickybeaks of all stripes, I herein explain why the metric system is inferior to traditional systems of measurement for those who work with their hands, think with their right brains, and prefer not to resort to a calculator for every little thing.

Metric vs. traditional systems

First, I don’t like the term “metric system.” Either it refers only to the meter and ignores all of the other units of measure (which is silly), or it implies that it’s the only system that is metered (which is also silly). What is commonly called the metric system is part of a much larger system of measurement known as the International System, or SI. (The abbreviation is backward because it comes from the French, and they do everything backwards.)

The SI is all decimal, and its units, which include familiar ones like the watt and the second and less-familiar ones like the joule, are all interrelated in a very nice way that I won’t trouble to explain here. (You can read about it here.) It’s a very nice system, for many purposes — but not for all purposes. (I’m unnecessarily familiar with it from having been, at some time late in the last century, a theoretical physicist in training.)

Traditional systems of measurement, including the English or Imperial system, evolved over centuries or millennia to meet the needs of specific cultures and crafts. They are distinguished from the SI in two important ways. First, instead of having a single standard unit for each kind of thing you can measure (e.g. the meter for distance, the liter for mass), they may have several named and defined units for each quantity (e.g. the inch, foot, yard, and mile for distance; the teaspoon, tablespoon, cup, quart, gallon,etc. for volume). Second, they are not based on a decimal system (base ten) but typically on multiples of two and three. That is, units are divisible into one another by two, by three, or by multiples of two and three, rather than by ten; so the foot is 2×2×3 inches and the tablespoon is 3 teaspoons.

Advocates of the SI argue that both of these differences weigh in the SI’s favor. Standardization is useful if you’re dealing with international trade and industrial-scale production, and a decimal system is useful if you’re dealing with large numbers, doing complex calculations, and relating units to decimal money. Again, for many purposes, the SI is ideal.

But for the purposes for which traditional systems were designed, I believe they are still superior. They were designed to be used in craft, in work done by hand, by people who might have had little or no formal mathematical ability and who were not doing complex calculations on paper (let alone with a computer). Arithmetic in handcraft is done mentally, and thus should be as simple as possible. That’s as true now as it was a hundred or a thousand years ago. If you’re cooking, for example, and you want to make half a recipe, you don’t want to have to go and get a calculator to figure out how much flour you need. If you’re building a piece of furniture and want to space stiles or screws evenly, again, you should be able to do it in your head, or with a minimum of figuring on paper.

Traditional systems of measurement are better for handcraft and mental arithmetic for both of the reasons they’re different from the SI. The hodgepodge of units seems like a lot of trouble to learn, but once you learn the units needed in a particular craft, you realize how much sense they make. You find that there is often a named unit for quantities that you tend to need frequently, and that various units are spaced at intervals that make them convenient to use. They relate to orders of magnitude that are more useful on a day-to-day basis than orders of ten. (Are you really going to tell me that a three-digit number of milliliters is easier to deal with than a tablespoon?)

More important, I think, is the fact that traditional systems are based on twos and threes. They’re designed this way for a reason: human beings think in twos and threes. Yes, we have five fingers, and so we can easily count to ten, and so we developed a decimal system of numeration. But we don’t really think in fives.

I’ll give you two examples. First is a participatory example. Take a piece of paper and fold it in half. No problem, right? You just thought in twos. Now take a second piece of paper and fold it in thirds. It’s a little harder to get it accurate, but you can still do it. You just thought in threes. Now take a third piece of paper and fold it in fifths. No measuring — just eye it up and do it.

You can’t. Unless you have some extraordinary mathematical visualization skills, you can visualize halves and thirds, but not fifths.

Second example: music. Musical meters are virtually always in two, three, four, six, eight — multiples of two and three. Just as we can visually divide a piece of paper in halves or thirds, we can mentally divide a beat of time in halves or thirds. And music in five and seven time is extraordinarily rare, because it’s as difficult to hear fifths and sevenths as it is to visualize them.

This is why traditional systems of measurement use multiples of twos and threes. Multiples of twelve are almost perfect; you have two twos and a three: half a foot is a whole number of inches; a third of a foot is a whole number; half of half is a whole number of inches. A third of a meter is what? A mess. Sure, you can take a fifth or a tenth, but when, in ordinary, utilitarian work, do you ever actually need to divide something in fifths?

You might think that using a decimal system of measurement would encourage people to divide by five, but it doesn’t. Why, for example, are bottles of wine 750 milliliters? It would be more purely rational to make them 700 or 800 milliliters — only one significant digit, as scientists would call it, instead of two. But we don’t do it that way; we use a three-digit number with two significant digits to refer to a volume that is three-quarters of a liter. Three quarters of a liter is nice and neat and simple. Seven hundred and fifty thousandths of a liter is just silly.

One of my favorite units of measurement is the pica. Everyone who has used a word processor has seen point sizes — twelve point type, for example. There are twelve points to the pica and six picas to the inch. This is a system designed for visual layout. Now that I’m using a computer, you’d think it would be easier to use millimeters, right? But it isn’t, because you never lay out a page in fifths. Look at magazines: how many (evenly divided) columns do they have? Two, three, four, six, sometimes twelve with overlapping text. Never five. Never. It just doesn’t look right. People don’t think in fifths. That’s why, even when the computer could do all the decimal math for me, I (and other designers) still use picas and points. They’re more appropriate to the task.

My point is that our systems of measurement should reflect the way we think — not the other way around. If you’re doing rocket science, the SI is fabulous. I’ll concede that it also has broader application in trade than most Americans would allow; if I’m buying 9.6 gallons of gasoline, the point of using a gallon (which is 4 quarts, 4×2 pints, 4×2×2 cups, 4×2×2×8 fluid ounces, 4×2×2×8×2 tablespoons, 4×2×2×8×2×3 teaspoons — all easily manageable twos and threes) is lost. The computer is counting it for me and converting it to dollars; let it be decimal liters.

If I’m cooking or building something, though, leave me my feet and inches and teaspoons. They’re more appropriate; they’re easier to use; and they fit themselves to ordinary human thought rather than forcing people to adapt themselves to a scientific method. So what if the decimal system and all those prefixes are elegant? I don’t care whether a system of measurement is elegant. I want it to be useful.

I think that a lot of Americans’ resistance to the metric system stems from two roots: one, they don’t care how elegant the damn thing is as long as it works, and two, they don’t give a damn how everybody else in the world does it. In particular, they don’t like a bunch of experts telling them that the way they’ve always done things is stupid. It isn’t that they’re a bunch of slack-jawed yokels who are resistant to change; it’s that the metric system does not present them with a better alternative to what they already have.

The loss of traditional units of measurement, I believe, corresponds with a loss of cultural know-how. It corresponds with the replacement of craft by industry, of self-reliance by the rule of experts, of an intuitive understanding of the world by rationalism, and of diversity with universal decree. None of those changes is an unfettered good, and beyond a certain point I’m not sure they’re good at all.

If experts want to rationalize things, they could give us a base-twelve system of numeration, and then this would all be simpler. But I’d rather the experts stay out of it and stop trying to dictate how people think. Leave people alone, and they’ll use whatever system makes the most sense in a given context. Systems will evolve and improve to meet new needs. That’s what diversity means: you let people do things differently, in part because that’s how new and better ideas develop.

I’m willing to trust diversity and let cultural evolution take its course. But either way, I’m keeping my picas.