On 2011-07-16 advocates of U.S. metrication lost one of their greatest friends: Pat Naughtin, of Metrication Matters . In his untiring efforts to introduce the metric system to Americans, not as something to be feared but as an amazing benefit, he should be counted among the nation’s greatest unappreciated friends.

Pat Naughtin was an expert in the psychology of measurement. He was, as he was quick to point out, not at all the right person to consult on the purely technical aspects of measurement, such as the calibration of scientific instruments. Instead, he was fascinated by questions of why people measure in certain ways, why these are often awkward and counterproductive, why people often resist adopting better ways, and how they can be helped over such mental hurdles.

It is a field in which there are very few, if any, other experts. In fact, although he was far too modest to make such a claim, it is hard to think of him as not having invented the field. And it is an important field. The Australian conversion to the metric system was probably the most successful national metrication ever accomplished: every industry involved, all work essentially completed within a single decade, the 1970s, and all done without any of the social disruption and mental anguish which Americans have been taught to fear by our political classes. That this was done so easily was in large part the result of attention to details and methods which Pat studied and promoted so effectively.

Pat was not the kind of person to formulate anything so pretentious as a set of precepts named after himself. But it is impossible to read through the written material he left behind, and listen to his recorded presentations, without noticing that certain simple and elegant principles occur throughout. Here at the Metric Maven, we will be exploring these, in detail and diverse ways. Since they will be referenced often, it seems good to give them names at the start, and summarize them in a single, prominent place. And since Pat was, whether he would claim them as his own or not, at least their most effective contemporary advocate, it also seems fitting to name them in memory of a fine and generous gentleman. Here then, we propose Naughtin’s Laws.

Naughtin’s 1st Law: Dual-Scale Instruments are Evil

Don’t let the word instrument put you off: a ruler, a measuring cup, and a kitchen scale, are all instruments. One might suppose that a dual-scale ruler, inches down one edge and centimeters down the other, would be an excellent teaching device to accustom a non-metric user to metric measurement. In fact, it has the opposite effect: as long as the familiar scale is within the user’s field of vision, the unfamiliar scale might as well be invisible. To make matters worse, what most Americans think of as the centimeter edge of a ruler is almost always a millimeter scale numbered as though it were a centimeter scale. This is just sad.

Currently, this is a hard rule to apply consistently in the U.S., because well-designed purely metric measures are almost impossible to find. This is particularly the case in kitchen measures. One can find measuring spoons with metric markings, but these are usually smaller than the imperial markings, and the numbers make it clear that the metric markings are an afterthought. A tablespoon, for example, may carry the secondary legend of “15 mL,” or even “14.7 mL,” as though recipes regularly called for such awkward amounts. Kitchen scales are almost always dual-scale devices, but at least the better ones today “remember” the scale last used when activated. There may, however, be some so poorly designed that they always “wake up” in their imperial mode and have to be reset every time. The Metric Maven strongly supports recycling such nightmares at your nearest electronics recycling center.

Naughtin’s 2nd Law: Prefer Measures Without Decimals

Decimals are wonderful. If given the choice of using decimals or fractions, what sane person beyond grade school would not prefer decimals? You can look at two decimal numbers, and immediately tell which is larger, something impossible to do with fractions of mixed denominators. But if both fractions and decimals can be avoided, why not do so?

One rather startling fact about the Australian metric conversion is that nearly all of their industries opted for the millimeter as their preferred unit of measure, including the construction industry. The plans for Australian houses are drawn up in millimeters. Why use something as small as a millimeter to design something as large as a house? Because decimal numbers are eliminated from the blueprints. Which means that the guy on the job site running the radial arm saw never has to deal with anything but whole numbers. Which means that he makes fewer mistakes. Which means that waste is greatly reduced.

Naughtin’s 3rd Law: Don’t Change Measures in Midstream

To give the simplest possible example, if you start out measuring things in millimeters, don’t feel obligated to switch to meters just because you find a few objects that go past the 1000 mark on the tape. Zeros are a good thing. They are your friends: you do not need to swap prefixes and shift decimals just to avoid zeros.

The most common wine bottle today is 750 milliliters. What then should we call a bottle exactly twice that size? For a number of reasons, including the fact that it would make the columns in the shopkeeper’s inventory spreadsheet more readable, because it saves the customer from the mental effort of shifting a decimal, and because it precludes the need for a decimal at all (see 2nd Law, above), the Metric Maven strongly advocates 1500 milliliter wine bottles (and responsible consumption). Wine bottles in this size, however, are usually labeled 1.5 liters. Wine shop advertisements may flip-flop between liters and milliliters, decimals and whole numbers. This is not, for once, a matter of U.S. metric obstructionism, but a matter of worldwide metric obtuseness. Even metric countries could do metric better.

It’s also possible to find examples of switching measures within a single measurement. In the strange phenomenon of “unpacking,” a single number may be broken into two or more numbers, or more than one prefix may be applied to one number, and the author may actually believe this makes things clearer. The deprecated metric prefixes around unity (see 4th Law, below) encourage this error: “125 mL” may become “one deciliter, and two centiliters, and five milliliters.” This sort of awkwardness may be acceptable in non-metric cookbooks (“now add one cup and two ounces…”) but it’s unnecessary in metric.

Naughtin’s 4th Law: No Centimeters!

Actually, no centi-anything. Also, no deci-anything, no deca-anything, and no hecto-anything. But the centimeter is far-and-away the most common violation of this rule, and the only one most of us ever hear much of, so it gives its name to the law. The system of metric prefixes is, ultimately, a fantastically useful device. But the inventors did go a bit crazy by placing a tight cluster of prefixes around the number one. There are metric prefixes for tens and tenths (deca and deci) and hundreds and hundredths (hecto and centi). These should be forgotten. They convey much less information to the mind than an extra zero. Quick, which is more: 1 mL or 1 cL? Yes, I’m sure you got the right answer, but I’ll bet there was a moment of thought. Which is more: 1 mL or 10 mL? Now wasn’t that easier?

Drop these four prefixes, and there are only two remaining that non-technical people will ever have to deal with commonly: kilo for thousands, and milli for thousandths. Conversions between measurements become almost unnecessary, and on the rare occasions when they do crop up, there is one and only one conversion factor to remember: 1000.

These four laws, or rules or precepts if you prefer, can be taken as a kind of style manual in embryo for metric usage. As with any language or tool, the metric system can be used well or poorly. Pat Naughtin promoted metric usages designed to simplify rather than complicate, communicate rather than obfuscate, encourage rather than daunt the well-disposed, and persuade rather than alienate the ill-disposed.

Thank you, Mr. Naughtin.