10-26-11 - Tons

In the US, a "ton" = 2000 pounds.

In the UK a "ton" is 2240 pounds (which comes from twenty "hundredweights" where a "hundredweight" is eight stone, and a stone is 14 pounds, WTF Britain).

A "metric ton" is obviously 1000 kg. In the UK this is officially called a "tonne" which you will see in technical documents, but I don't see that used much in casual writing, and it's certainly confusing when spoken since it sounds the same. (but a UK ton is very close to a metric ton (2204.6 pounds) so the mixup here surely happens all the time and is not a huge problem).

(when you hear someone in the UK phonetically say "ton" do they mean "tonne" or imperial ton?)

To differentiate the US ton vs UK ton they can be called "short ton" or "long ton".

On a related note, a pint is not a pound *anywhere* in the world.

In the UK, 1 oz by volume of water = 1 oz of weight. But a "pint" in the UK is 20 oz. So a pint is 1.25 pounds (a gallon is exactly 10 pounds)

In the US, 1 oz by volume of water = 1.041 oz of weight, so a pint = 1.041 pounds. (and a gallon = 8.33 pounds).

(neither liquid ounce is anything neat in terms of volume; the only nice whole number unit is the US gallon which is 231 cubic inches)

(the weight measures are the same in the US and UK, it's the US volume measure which went weird (1.041), and I believe it was done in order to make the gallon an integer number of cubic inches)

If you want to get technical, a (US) "pint's a pound" at some high temperature. (...some digging...) actually it's very close just before boiling. It looks like 98 C water is almost exactly a pound per pint (US).

Actually there is a sort of cute book-end of the ranges of water density there :

Very close to freezing (4 C) water is 1 g/ml , and very close to boiling (98 C) it's a pound per (US) pint. The difference is a factor of about 0.96.


Mezz said...

The UK is a slightly bizarre mixture of metric and imperial measurements. Produce in shops/supermarkets is labelled metric (grams, litres etc.) but sometimes the quantities which match imperial ones. For example, we buy 568ml cartons of milk. Other things - mainly depending on some kind of inertia or laziness - use imperial quantities. For example, we get 'miles per gallon' stats in car advertisement, despite fuel at the pump being priced and measured per litre. However, all the road signs and speed limits use miles rather than kilometres. We do however get a 'CO2 emitted per kilometre' stat, but the only reason to give a shit about that is that the government bases their vehicle taxation on that (rather than actual efficiency). If you go into a pub, you still ask for a pint of beer, but spirits are given in measures of 25ml. Fuck me sideways.

Mezz said...

Addenda: I've never heard somebody say 'tonne' and mean the imperial measurement, they mean 1000kg. Which incidently, all car masses are given in. Though most human weight scales measure in stones and pounds.

cbloom said...

"Which incidently, all car masses are given in."

Not true! I did a quick scan of evo or autocar or something when I was writing this and I found that a lot of their "bhp per ton" figures were for imperial tons. And in general they seem to mostly use "tons" not "tonnes".


(there are mistakes in it too; for example the Honda NSX bhp per ton was done with metric tonnes; the vast majority are imperial tons though).

The official manufacturer stats seem to all be metric tonnes though. eg. the Caterham R400 is named for 400 bhp per *tonne*. All the press releases seem to be tonnes.

Mezz said...

Oh sorry, my poor on clarification - I meant when looking at the mass (in a brochure/whatcar etc.) that they'll give it in kilograms. It's even like this on your link - then in the column right next to it they state the power:weight in bhp/ton!

old rants