A Kilotonne is How Much in Metric?

By The Metric Maven

Bulldog Edition

When I was in college, I studied Electrical Engineering. I was told many times that one was no longer to use concatenations of metric prefixes, this was considered very bad practice. What this meant was that one should not use two metric prefixes concurrently to designate values. At that time there were capacitors which were marked micro-micro Farad (μμF). Micro is 10-6 so two of them together would 10-6 *10-6 or 10-12. There is a perfectly good metric prefix called pico to describe this small amount of capacitance. The slang term is puff. So these μμF capacitors should be described as picofarad pF capacitors. This made perfect sense to me. I was surprised that such an ad hoc nomenclature would make it into engineering or be tolerated. When I took my first job, we used a device called a directional coupler to calibrate the power level of measurements. The coupling factor for the directional coupler was shown on a graph which was on an attached metal plate. The coupling was different at different frequencies and the graph was used for correction. The frequency axis of the graph said KiloMegaCycles. I knew this designation was from a long time back as cycles per second had been called Hertz for decades. I found this antique item to be a source of humor for me.  Who on earth would write a frequency in Gigahertz (GHz) [109] as (KMHz) [103 *106 = 109]. How on earth did that make sense? What I didn’t realize was that the US “do your own thing” anarchy of weights and measures allows, and seemingly promotes this type of designation.

Imperial and US Olde English unit usage have been retained in the metric system, and have never been purged as they should have been. I’ve spent considerable time expressing my views about the centimeter as a pseudo-inch, (and have condemned the entire prefix cluster around unity), but there is a much more sinister and in-your-face Imperial/US Olde English holdout in the metric system. It is the tonne. The fact that there is an extra n and e should make one think Ye Olde English metric. The designation tonne is actually an approved usage!  The tonne is properly called the Megagram or 1,000,000 grams, but when used in a completely feral manner they are known as metric tons—no extra n or e, just pigfish. So what is a metric ton? Well it’s 1000 kilograms, or 1 kilokilogram (KKg). It turns out that 1 kilokilogram is close to a short ton (0.907 kilokilograms). A ton is probably derived from a tun which was the weight of a barrel of wine. So why was it so important to taint the metric system with an unnecessary non-metric-metric unit? Had someone been drinking? Worse yet the metric ton is just another way of writing kilokilogram and pretending it isn’t poor usage. If I wrote something has a mass of 97 kilokilograms I’ll bet most pro-metric people would wrinkle their nose and pitch a small fit, but If I said 97 tonnes or even 97 metric tons, well, only the tinkling of ice in glasses around the metric table would be audible. How about K2g for metric ton?—I’ll bet that wouldn’t go over well either. So why is tonne or metric ton acceptable in polite company?

This blog was originally to be about Naughtin’s Laws and the press. I was curious about how “professional”  people talk about large quantities. Well, it turns out that there are many varied and mangled ways that this is done by journalistic denizens of the only country which embraces US Olde English Units. I was curious about the amount of metals produced world-wide, and found a slide presentation with this table:

When my mind encountered the word kilotonnes, it seized up for a moment and I experienced metric vertigo. Kilotonnes!!!  So in other words the amount of metal is being described is in terms of kilokilokilograms or KKKg! That sounds rather ominous—perhaps K3g would be better? Let’s see what would that be in non-pig-Latin metric? Oh, it would be simply Gigagrams. This is not to be confused with Gt which is proper pig-Latin metric for Gigatonne or in improper pig-Latin metric is K5g . The source of this table will remain anonymous. There is no need to single out this person, he never chose to be in the spotlight. But news items which are written by “Journalists” for the public, well, I’m less inclined to invoke a Metric Maven Client privilege. Lest you think this usage is uncommon, the article Great Balls of Fire in New Scientist on 2013-06-29 (page 42) describes the explosive impact of meteors in megatonnes and kilotonnes.  Here are some values in terms of metric tons I randomly found on the web using a google search:

  • Mining operations in Amapa, where Anglo American produced 6.1 million metric tons of iron ore in 2012
  • According to Philips estimates, using the LED replacement could also eliminate 11 million metric tons of carbon emissions annually, or the equivalent of removing over 2 million cars from the road.
  • This clean solar generation plant will displace the equivalent of approximately 54,000 metric tons of carbon dioxide (CO2) per year, which is equal to the amount that roughly 2.2 million trees would displace annually
  • “The ground fish fleet is a huge contributor to local port economies,” he said. “In my district alone, on any given year, you will have a dozen trawlers that contribute 10,000 metric tons of fish and that represents about $20 million worth of product,” he said.
  • The Wikipedia article referenced below indicates that the Earth has around 40,000 Gt of carbon in the hydrosphere, biosphere and atmosphere
  • More than 2,000 farmers in six communities in the Northern Region will benefit from a 500 metric ton certified warehouse for grain storage at Datoyili, in Tamale.
  • From July-February 2012-13 about 5,590,775 metric tons of cement worth US$ 376.85 million exported as compared to 5,589,372 metric tons valuing US$ 303.71 million of corresponding period of last year.

Do you really have any idea of the comparative magnitudes offered in these news stories? I would bet not. Let’s try to get a handle on these values using Naughtin’s Laws (mostly) and Metric Prefixes.


Article Value

Metric Value

Iron Ore

6.1 million metric tons

6.1 Teragrams (1012)


11.0 million metric tons

11.0 Teragrams (1012)


54,000 metric tons

54.0 Gigagrams (109)


10,000 metric tons

10.0 Gigagrams (109)

Total Carbon  (Eco System)

40,000 Gigatonnes

40.0 Exagrams (1018)

Grain Storage

500 Metric tons

500 Megagrams (106)


5,589,372 Metric tons

5.6 Teragrams (1012)

There is no excuse for Americans not to have an idea of the relative magnitudes of Mega, Giga and Tera. Computer disk drives were in Megabytes, then as they became larger they came in Gigabytes, and now one can buy external hard drives of 1-2 Terabytes without a problem. Peta–well, that’s way big, but one can look it up online without a problem if needed.

The presentation of quantities using metric tons only obfuscates a person’s ability to immediately compare them. It also in many cases can serve to obscure the decimal nature of metric values and money. For instance here is the pricing of copper in one article:

  • Benchmark copper on the London Metal Exchange (LME) hit a session low of $7,439 a metric ton (1.1023 tons), its weakest since August 21, and closed at $7,465 a metric ton…

We note that the price is given in metric tons, and then they provide a conversion factor for US Olde English short tons. Let’s see, copper costs $7,439 per metric ton; how could we possibly compute the price of other quantities?  I have an idea, perhaps actually using the metric system might help?  How about $7,439 per/megagram, or $7.43 per kilogram, or 74 cents per gram. Look ma!—no calculator! The metric ton designation really screws up the simplicity of decimals, which is one of the reasons metric was adopted internationally in the first place. Seriously, the metric ton is just a tonne of problems, it should have never been accepted as a legitimate usage in the metric system. It only serves to obscure, and that means that for unscrupulous persons, it’s used for dishonest purposes. It’s not a metric ton, it’s a Megagram! Members of the press—learn to count!—by using the metric system!

Correction 2013-12-20 Total carbon corrected to Exagrams.

17 thoughts on “A Kilotonne is How Much in Metric?

  1. While on the topic of using prefixes correctly, would you please stop capitalising the k symbol for kilo? k should always be lower case for kilo, never uppercase. They are case sensitive, as you should be aware from other prefixes like M for mega and m for milli.

    • I’m not able to promise I will use a lower case k. I really don’t like it. It only makes sense that prefixes which magnify would be upper case and those which divide should be lower case. It would (should) be a nice simple logical rule. I find the lower case exception for deca (da), hecto (h) and kilo (k) as incongruous, and complaints about my lower case violations as nothing but a yocto-peccadillo. All the other magnifying prefixes are capitalized, and make sense, k for kilo does not. In the past I have used all upper case as a protest to what I find to be an irrational inconsistency. I often try to comply these days so I don’t get comments, and have people zero-in on this detail and ignore my larger point, but I don’t get exited if I do it the way I believe it should be done—and often don’t notice I have done it—as it makes sense to me. In short I think this usage should also be changed—like the megagram should be used for “metric ton” or tonne. Megagram tells you everything in words, tonne obscures. Micrometer tells all in words, micron does not. Nanometers tells all in words, angstrom does not. K implies magnification, k does not.

      • Wow, I just lost all respect for you. I’ve been following your blog for a while, and I generally agree with what you’re saying. But this makes no sense to me. You’re actually advocating inventing our own prefixes (such as you have done for “Kilo”), if we don’t find the SI one “logical”? How is this any different from using the tonne instead of the Mg?

        I’m European, so the SI system is the only one I’ve ever used (apart from some university textbooks using cgs). And I’ve never thought of the capitalization of prefixes as signifying “magnification”. You seem to be confusing objective facts with personal feelings.

        • This is true. But is it not also an example of argumentum ad hoc? Think of the far more dangerous problem of lower-case m.

          In SI, lower-case m, standing alone, means meter—or metre, if and as you prefer. But placed in front of some other unit, it becomes milli-. And yet I can’t recall a case in which anyone has complained that this introduces confusion. (And how often are non-scientists and non-engineers confronted with degrees Kelvin? Also, for some curious reason, it’s very uncommon to see a metric prefix in front of Kelvin.)

          Incidentally, Pat Naughtin makes the same argument, although I can’t find the reference at the moment. As much as we admire Naughtin, this may be a rare instance in which his usual independence from conventional thought may have deserted him. Oh, well: none of us are completely consistent.

    • Yes, the prefix for kilo is officially a lower-case k, but we here at MetricMaven.com have never been respecters of officialdom. Isn’t that obvious by now? In one form or another, it is the single issue that has gotten us into more hot water than any other in our brief existence.

      If you drop what the Maven calls the “prefix cluster around unity,” i.e., hecto-, deca-, deci-, and centi-, then there is an obvious and extremely useful rule that may be applied: upper-case prefix abbreviations magnify, while the lower-case diminishes. The only exception, and it is a puzzling one, is the abbreviation for kilo-, a lower-case k.

      The exception can be explained historically, but why bother? Why not just accept a further, and obvious, rationalization of the SI system, and say that all prefix abbreviations that magnify should be upper-case, while all lower case abbreviations reduce?

  2. Check your Total Carbon (Eco System) conversion. It’s 40*10^18 or 40.0 Exagrams.

  3. In biology lab in my sophomore year in college, I had to work with infrared analysis. The teaching assistant, among others, used to refer to infrared wavelengths in “millimicrons,” a “unit that contained both a concatenation (10^-3 and 10^-6) and a misnomer (micron; should be micrometer). Along came a different T.A., one better versed in SI, and introduced the term nanometer and its symbol, nm. What an epiphany for me! In terms of naming the unit, made a LOT more sense. The proper use of the SI suddenly came into view.

    I think that there are many people who have never been schooled in the SI, and also many people who, as you rightly note, Randy, still like to form metric units in the image of their legacy units. That is, they think in terms of “to a,” as in “12 inches TO A foot, four quarts TO A gallon.” They do not yet feel comfortable measuring with the decimal-prefix logic of the SI.

  4. According to a historical article on the NIST website, only prefixes from micro to mega were being used from 1874 forward (to 1960??). Also the micron was approved in or before 1948 for what we now call the micrometer. The lack of suitable prefixes led to micromicrofarads, millimicrons, kilomegacyles, etc. In 1960, as part of the definition of the SI, prefixes were expanded from pico to tera (and later expanded to the present set).

    The concatenated prefixes took longer than necessary perhaps to fall from usage, but they were not feral, they were part of an earlier metric system. We should not be surprised by them or mock them in a historical context.

    What is feral is personally deciding that prefixes and symbols as issued by the BIPM should be modified for personal preference like capitalizing K, H, D for kilo, heco and deka. Once the BIPM has settled the issue, we should use the standard or soon there isn’t a standard.

  5. There is a post on this subject from the dozenal forum called:

    Customary Never Went Away, it merely changed units


    I was thinking of copying the original comment here, but it is very long. So it is best to go to the forum and read it there.

    Once you read it, you will see that this situation is world wide. The author’s “solution” is to abandon decimal and SI and go dozenal. The real solution to the problem is proper teaching so that old habits are broken and the most efficient way to use SI is thru proper teaching, which obviously is not happening.

    We are taught that the earth is 149.5 million km instead of 149.5 Gm. We stick the word million instead of scaling the prefix to avoid this word.

    The BIPM needs to be more involved in the proper teaching and usage of SI. It is already frowned upon to use double prefixes with units and that practice seems to be gone, but the practice of inserting counting words between numbers and units still needs to be addressed.

  6. Despite the fact that the correct unit is the megagram, we are stuck with the tonne for some time. The BIPM even recognises it as one of the units acceptable for use with SI, simply because it has a 1:1 relationship with an existing SI prefixed unit as does the litre (=1 dm^3) and the bar (=100 kPa).

    The only problem with the tonne that creates confusion is the fact that the US NIST has a bug up their arse with the spelling and absolutely refuses to accept the “ne” on the end of ton. They can’t call it “ton” as that would result in confusion with the short ton often called just ton. So they decided to add the word “metric” in front of ton implying a derivation from the “true” ton of 907 kg.

    This has caused some confusion when those that don’t know better add the prefix “metric” to tonne, when the spelling “tonne” already implies 1000 kg. It is as if the US does this in an attempt to sabotage SI.

  7. About the tonne, an interesting discovery (I didn’t know that there once existed such a system):


    MTS seems to be good for (heavy) industrial use, while CGS was better for laboratory science; and today’s MKS of course lies somewhere in between, thus being probably the best choice for everyday use: for example, it would sound really strange to buy a millitonne of apples, while one kilogram is definitely better, on this front…

  8. …. Except – and it is a big except – for the absolutely irrational fact that the kilogram is a base unit containing a prefix: which is probably one of the reasons why the megagram isn’t used that much (not the only reason, of course).

    I don’t understand why the name of the kilogram has’t yet been changed, after decades of discussions; certainly the proposed alternative names (bes and gio) weren’t good enough, and this is understandable: but there could have been other name proposals, which sadly hasn’t been the case.

    The SI – otherwise quite rational – will contain a heavy irrationality factor, until this question will be solved; personally, as I said some time ago, I’d just redefine the (heavy/new) gram to be the kilogram, which would be rather easy.

    Or, in a reverse way, redefine the (light/new) ton(ne) to be the kilogram; or, even better, find some other name, but an intuitive one, not something derived from names or thing if the past that nobody knows (I.e., no scientists’ self-referential elitarianism, please!).

    But sadly probably nothing will change, at least until the SI remains too customary (sic!) in its inherited habits.

    Anyway, an “SI 2.0″, with some radical reforms like the above one, would be a very good thing, IMHO…

    • BTW, thinking a little more about all this, the “old” and “industrial” MTS seems to be more rational, as 1 tonne is essentially 1 cubic meter of water; while in MKS 1 kilogram is essentially 1 cubic *deci*meter of water, thus – besides being a base unit with a prefix – also implying one of those prefixes (centi-, deci-, etc. etc.) that probably should be avoided, at least officially.

      MTS would also solve the problem of the renaming of the kilogram: no renaming would be necessary, as the tonne would be the new base unit for mass.

      From an industrial point of view, it would be an excellent system…

      While in everyday use, people would probably gradually become accustomed to the change, with time (exactly as it would be with metrication, in the US).

      Too radical and maybe also impractical? Who knows – just an idea, anyway, stimulated by this very interesting article (otherwise, I’d probably never have thought about these problems)… ;-) :-)

  9. Sorry, I forgot that you talked about the MTS system in a recent article:

    “To confuse matters further there was also another mts, the meter-tonne-second system, which thankfully is now but a historical curiosity. These systems seem to have invoked a strange version of The Implied Precision Fallacy. The idea was that mts is for industry and cgs is for laboratory work, but thankfully SI became the system for all to use—well except in one country.”

  10. Of course, what I meant before was that the MTS system would be more rational if it were the only system (no CGS, no MKS), thus superseding the current SI, with its irrational kilogram derived base unit (and also the liter as a cubic decimeter – instead of a cubic meter! – of water)…