The Metric Bishops

By The Metric Maven

Seventh Anniversary

The BIPM SI Brochure is the divine canon of the metric system for many. At the beginning of the English section (the French version is repeatedly stated to be the official version) we read:

The SI is, of course, a living system which evolves, and which reflects current best measurement practice (pg 101)

Well, “of course” it is, and like those who argue for the divine perfection of Ye Olde English, they claim that as a product of technical Darwinism, the metric system has slowly perfected itself through some unspecified Darwinian magic. This appears to provide cover for questionable decisions by very human, human beings. The metric system as everyone knows, uses magnifying and reducing prefixes to describe the size of a metric unit based on the concatenation. All of the single letter symbols (in triads) are upper case. For example Mg, GHz and Tm all are upper case. But there is an exception, and the SI Brochure states it:

As an exception, the name of the kilogram, which is the base unit of mass, includes
the prefix kilo, for historical reasons. It is nonetheless taken to be a base unit of the SI.
The multiples and submultiples of the kilogram are formed by attaching prefix names
to the unit name “gram”, and prefix symbols to the unit symbol “g” (see 3.2, p. 122).
Thus 10–6 kg is written as a milligram, mg, not as a microkilogram, μkg.

Ok, for “historical reasons,” not techincal ones, the kilogram is a base unit. For some unexplained “reason” the magnifying symbol for kilo is a lower case k. The prefix hecto, h, and deca, which has a two letter prefix da for unexplained “historical reasons,” are both lower case, yet both are magnifying factors of 100 and 10 respectively. What is the rational for kilo?—to keep hecto and deca from becoming lonely? As near as I can tell, there is no explanation in the SI Brochure, it’s just part of the divine doctrine. I see exactly no reason the symbol for kilo is k, rather than K. The kilogram is only one of many potential kilos; kilopascal, kilometer and so on must be kp and km for some unexamined “historical reason?” I’m speculating, as the SI Brochure appears silent on the subject.

The kilo exception is so unnatural, that very often I see people use capital K without thinking about it for a metric magnification symbol, why wouldn’t they? All the others are capitalized, why on Earth would they expect it to be otherwise.

In section 3.2 it is stated:

Among the base units of the International System, the kilogram is the only one whose
name and symbol, for historical reasons, include a prefix. Names and symbols for
decimal multiples and submultiples of the unit of mass are formed by attaching prefix
names to the unit name “gram”, and prefix symbols to the unit symbol “g”

So the gram is a sort of virtual base unit? The SI Brochure is clear about the concatenation of prefixes and in a gloss it states:

10–6 kg = 1 mg, but not 1 μkg (microkilogram)

But it is okay according to this sacred text to write a kilomegagram as a kilotonne?

It is when Section 5 of the BIPM SI Brochure describes how to write metric units in prose that I want to use the Holy Hand Grenade of Antioch on it. Here is what they have to say:

Unit symbols are printed in roman (upright) type regardless of the type used in the
surrounding text. They are printed in lower-case letters unless they are derived from a
proper name, in which case the first letter is a capital letter.

I find this assertion only satisfies the dogmatic desires of English teachers who have read the revealed truth of capitalization in another sacred text, and no more thought is allowed. Those who disagree?—–there are rulers applied to open palms for those who question this lower case requirement to pass your class.

I have long asserted this set of “English rules of grammar” decrease understanding and only produce magnitude confusion. An officer of a well-known metric organization viscerally rejected the notion that children in grade school, middle school, and high school should be required to memorize the metric prefixes (excluding the prefix cluster around unity (PCAU), i.e. hecto, deca, deci, and centi). We are immediately instructed to learn the 26 letters of the alphabet, have a song, a, b, c, d, e, f, g…..tell me what you think of me; that the youngest in our midst are expected to learn. There are sixteen metric prefixes. Certainly we can figure out a song; we do for the days of the months. Why is full metric in education so off limits?—even to persons who see themselves as metric promoters?

It only makes sense to me that all the magnifying prefixes (excluding the PCAU) should be capitalized, whether as symbols, or as words. It will be Kilogram, Megameter, Gigahertz, Teraliter, all the way to Yotta. The reducing prefixes?—all lowercase, millimeter, microliter, picogram. The less familiar units are expressed in a manner that will provide hints of their reduction or magnification. For instance which is the magnifying prefix, or reducing prefix: zepto or zetta? atto or exa? and as I will discuss this problem is only going increase. If I write these as zepto and Zetta, atto and Exa, it is immediately clear from the capitalization which prefixes magnify and which reduce. This makes perfect sense, but first the Metric Bishops lectured me concerning my blasphemy, then ignored my use of capitals, after pointing to the ecclesiastical document produced by the BIPM, and possibly determining my suitability for a metric auto de fe.

The BIPM appears to have adopted what English pedants have arbitrarily chosen in language antiquity, without any thought to the needs of the metric system. Proper nouns are more important than proper understanding? I reject this ridiculous dogma. There is only one situation where Kilogram is allowed (other than as the first word of a sentence) in the SI Brochure, and was first stated in 1889:

• the equality in length of the international Metre and the equality in mass of the
international Kilogram with the length of the Metre and the mass of the Kilogram kept in
the Archives of France;….

Only when we discuss the definite article, Le Grande K, are we allowed to capitalize, at least as we see usage in the SI Brochure. Soon there may not be a physical artifact. As there is no Meter any longer, there will be no Kilogram. Why not upgrade the English language and make its expression of the metric system meaningful, and not obscure.

Recently, there has been a proposal to add two more magnifying prefixes, and two more reducing prefixes. The BIPM clearly believes it has the right to coin words, if they coin them, why not adopt my suggestion of capitalization? Now which is the metric
magnifying prefix? ronto or ronna? quecca or quecto? Here is a list of the new set of metric prefixes, with the newly suggested ones:


I can see the utility of adding four more prefixes for a total of 20 (without the PCAU). I have written about values that are beyond Yotta in an earlier essay. What I see is that the BIPM is not living up to their assertion that the metric system is a living system. I’ve made it known that I see the pre-metric units as dead, but the glacial change of metric usage in language and symbols makes the metric system barely alive—if not currently in suspended animation. Perhaps with the suggestion of new prefixes, my suggestion that magnifying prefixes and words be capitalized, and reducing prefixes and words be lower case might be visited.

The SI Brochure has a very sanguine view of the metric system:

Because the SI is the only system of units that is globally recognized, it also has a clear advantage for establishing a worldwide dialogue. Finally, it simplifies the teaching of science and technology to the next generation if everyone uses this system. (pg 123)

That’s it? If the Imperial System was globally recognized, would it create a worldwide dialogue? Scientists and engineers are some of the worst at using the metric system. The reform of metric usage at the everyday level would help it bubble up to scientists I suspect. The use of millimeters, capitalization of magnifying prefix symbols and words, and lowercase reducing prefixes and words, the elimination of the tonne with the Megagram, the elimination of the micron for the micrometer should all be examined along with the addition of prefixes. It would make the metric system rationally evolve and prove it is alive. It would also make classroom instruction much more streamlined. As the US is essentially the only non-metric country left on this planet, its citizens will continue to suffer from the disadvantages the absence of the metric system produces daily, independent of what the BIPM decides.


If you liked this essay and wish to support the work of The Metric Maven, please visit his Patreon Page and contribute. Also purchase his books about the metric system:

The first book is titled: Our Crumbling Invisible Infrastructure. It is a succinct set of essays  that explain why the absence of the metric system in the US is detrimental to our personal heath and our economy. These essays are separately available for free on my website,  but the book has them all in one place in print. The book may be purchased from Amazon here.

The second book is titled The Dimensions of the Cosmos. It takes the metric prefixes from yotta to Yocto and uses each metric prefix to describe a metric world. The book has a considerable number of color images to compliment the prose. It has been receiving good reviews. I think would be a great reference for US science teachers. It has a considerable number of scientific factoids and anecdotes that I believe would be of considerable educational use. It is available from Amazon here.

The third book is called Death By A Thousand Cuts, A Secret History of the Metric System in The United States. This monograph explains how we have been unable to legally deal with weights and measures in the United States from George Washington, to our current day. This book is also available on Amazon here.