Related question: FAQ: On the use of a non-metric system

I was recently told on an answer by Oddthinking to specify that the "ton" I used in the answer to be a metric ton (or tonne).

However, I was under the impression that metric system was the default on this site, and it is the US-imperial short ton (2000 pounds) which should be specified when "ton" is used.

Is there a consensus on which form of "ton" is the default?

  • On an unrelated note, TIL that tonnage does not refer to the weight of a ship, but instead its volume. – March Ho Apr 18 '15 at 18:20

You should prefer metric units (I thought it obvious that you were, because you started with Kg).

And according to http://en.wikipedia.org/wiki/Ton and you should also spell it as "tonne" or "metric ton".

Also I might spell it "ton" out of habit, but I wouldn't mind if anyone edited it to "tonne" or "metric ton", to be less ambiguous.


Pedantically speaking, the SI/metric unit is the "kilogram". Ton is short hand for 1Mg, which is the correct unit, or also 1×103 kg.

Ton is also used in the US to represemt 907.185 kg, and in the UK to represent 1,016.04691 kilograms. So, imo, it's best avoided.

As a side note, the mile is also another "degenerate" unit:

  • International miles are 1.609344 km
  • U.S. survey miles are 1.609447218694 km
  • Nautical miles are 1.852 km

This is after 1959. Before that, there were dozens of different "miles" (which of course, makes it important to use the metric system as it's univocal, especially when dealing with old references).


metric system was the default on this site, and it is the US-imperial short ton (2000 pounds) which should be specified when "ton" is used.

I think there is some confusion here - we might be talking at cross-purposes.

SI units (or failing that, metric) is the preferred system, as per the FAQ you quoted.

That suggests, for example, that we should be sure to include metres instead of, or in addition to, yards.

However, it doesn't mean that we can, in the case of ambiguity, assume that the reader knows what we mean. So, it isn't safe to assume that an American reader (especially) will see the word "ton" and associate it with 1,000 kg.

But, in the case it is even worse, because "ton" isn't just ambiguous. It is (by only a small percentage) wrong in most areas.

In Australia, tonne and ton are different. Ton doesn't refer to 1,000 kg. I believe the UK (and most of the Commonwealth) is the same.

I understand in the USA, they prefer to use "metric ton" over "tonne", but "ton" still refers to the old-fashioned measure.

I have to emphasize that the error between the different measurements is small, and this precision was rendered irrelevant by the low precision of the original claim. I was being pedantic during copy-editing, and I was more worried about the lack of references than the error introduced by the ambiguity.

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