Metric & imperial weights
Pounds and kilos, grams and ounces, stone and tons (and tons, and tonnes)—Deciphering weights in the U.K.
Unlike the U.S., where only cocaine ever comes in kilos, in Europe you'll be ordering lots of (perfectly legal) things by the "key."
Actually, when it comes to food you'll more frequently order by the gram, because who needs 2.2 pounds (1 kilo) of anything?
Conveniently enough, 100 grams is just about the perfect amount, per person, of cheese, salamis and other cured meats, fruit, or whatever else you desire in putting together a picnic.
What about stones and tons?
When talking about their weight, many Brits will prefer to "stone."
1 stone = 14 pounds, so someone who says he's "13 stone" weighs around 182 pounds (or 82.5kg).
As for tons, things get a wee bit confusing (and it actually relates to the "stones" thing).
A "ton" in both the U.S. an Imperial systems is equal to 20 hundredweights.
Since an American (and Canadian) hundredweight is, reasonably enough, 100 pounds, a North American ton (sometimes called a "short ton") is 2,000 pounds.
However, since a British hundredweight is equal to eight stone (or 112 pounds), an imperial ton (or "long ton") is 2.240 pounds.
(Want to get more confused? There is also an unoffiical "tonne" in the metric system equal to 1,000kg, which is 2,204.6 pounds, 1.10 US short tons, or 0.984 imperial long tons. )
The Brits actually use both pounds and kilos, grams and ounces
Again, as with most things, Britain has split the difference on going metric here. Officially, all weights has to be measured in kilos and grams, but in practice people still frequently refer to things in "pounds."
No, you don't order a "112.5-grammer" at McDonald's in Europe; they know what a "Quarter Pounder" is. However, if I catch any of you giving into temptation and ducking into that McDonald's while you're in the U.K., so help me I'll verbally thrash you to within an inch...er, 2.54 centimeters...of your greasy fries-addicted life.
(The only tangential exception: You may go into the Burger King on the NE corner of London's Leicester Square, but only to use the bathroom and to climb to the second floor to snap a nice aerial picture of the square below.)
Actually, this point about Quarter Pounders was brought up by a greengrocer arrested in Britain a few years ago when jolly old England finally decided to crack down and force feed the metric system to its people. The bloke was still selling his bananas by the pound, not the kilo, at a local market so he was hauled off and fined.
The jovial fellow became something of a minor cause célèbre, the "Metric Martyr," and was fond of pointing out the hypocrisy that they would persecute a small fry like him when McDonald's was left to flagrantly flout the new laws by refusing to rename the Quarter Pounder.