That is what the metric system has brought us to. It should be whole grain mustard.
I tend to use imperial when I’m guesstimating or just doing rough measurements. As soon as I need to measure something properly, I switch to metric. I just find imperial easier for rough guesses - I can easily look at something and say ‘yeah, that’s about five foot’, but still can’t really visualise metres that well. It’s a result of my upbringing, I guess.
Really, the UK is a mess with this - in what other country would you be able to buy food in 454g measures? Another one is if you’re buying sheets of, say, plywood. They come in 2440 x 1220mm sheets. C’mon, really? They’re 8’ x 4’, just admit it. :rolleyes:
I reckon it’s going to be another 20 years or so before we’re properly switched over, and that’s even without converting our road system to km - that’s going to be massively expensive and a huge mess, so I have no idea when that will ever happen.
Pounds are best for losing weight, stones for gaining them. “I lost 70lb, but I put 5 stone back on”.
Why do people in the UK measure wight using stones and in the US weight is measured using pounds? And why do metric system users measure weight in kilograms rather than newtons, when kg are a unit of mass rather than weight?
Americans use metric system for energy content of food : calories (please do not nitpick I know it is kilo-calories). Americans also use Metric for bullet calibers - 9 millimeters 
Inertia of comfortable tradition. Expressing an amount in a scale that, for common values, remains in single or low double digits is nice and easy, so once established, is a hard habit to break.
“nine stone twelve” has a sort of easy verbal flow to it that “sixty-two kilograms” doesn’t.
Same for human heights - “five foot nine” has a ring to it that “one hundred and seventy-five centimetres” (or “one metre seventy-five” or “one point seven five metres”) seems to lack.
Of course, that’s entirely subjective, but that’s what humans are.
Because it works, and most of us never travel to other planets where the distinction makes a difference.
The answer to any of these questions is nearly always that the system has to be used by humans, who will always find their own balance between what is best, and what is most convenient.
Maybe what they’re measuring is, in fact, mass; they simply erroneously call it “weight”.
The kilogram predates the newton by nearly 150 years, and roughly 99.9% of us do not ever need to treat weight and mass differently.
Heh, we’ve done this in temperature, now weight. Next up: someone claiming a 15mm spanner would be more readily described as “a slightly less than 5/8 inch” spanner.
http://www.carolynrelei.com/inchchart.htm
When my wife and I honeymooned in Montreal, we went to the top of Mont Royal. We then called a cab to go back to our hotel. It was a rather harrowing ride down, akin to a thrill ride at an amusement park. I peered over the driver’s shoulder and read the speed. I then said to my wife, “I know kilometers are smaller, but isn’t 100 kph still pretty fast on a winding parkway?”
I’ve seen Americans make exactly that sort of claim, seriously.
Here in Australia, we use the metric system, but some US/Imperial units are widely understood. We know what feet and inches are, for instance, but temperatures usually need translation.
(Obviously it’s different for everyone and I’m making a generalisation, but this is the SDMB so someone will be along to pointlessly dispute what I just wrote any second now.)
I am not claiming any kind objective superiority of one form of words over another. I was explicit about that.
Habit and tradition are subjective things, but in the specific case of feet/inches for human heights, and stone/pounds for human weights, I think it is not hard to see why people were comfortable with non metric measures.
100% agree.
Celsius/centigrade isn’t really any more or less ‘metric’ than Fahrenheit. It’s a red herring in this discussion.
Celsius/centigrade is not fully metric, that’s true, but at least it is more “metric” than Fahrenheit in the sense that a temperature difference of 1 °C is the same as one of 1 Kelvin; and Kelvin is, in fact, the metric (i.e., SI) unit of temperature. When absolite temperatures, rather than temperature differences, are needed, then conversion from Celsius to Kelvin is necessary, but trivial.
It’s a sort of mix and match depending on what’s required for legal purposes and what people psychologically internalise as a comprehensible approximation to the size/quantity they want. For exact measurements and legal pricing, you might need 1200mm of a piece of timber, but you know the sort of shape and size you want as four-by-two. So that’s what you order.
(Just as in countries that have been metric for much longer, you will still hear mention of old quantities, like “une livre”,“une pouce”, “ein Pfund”, although what they’ll get is the metric quantity they approximate to).
Emphasis added. Of course. 38 sounds a LOT better than 97!! 
Variations of these posters, by U.S. citizens, presumably, float around the net: Imgur: The magic of the Internet and the more succinct Imgur: The magic of the Internet.
Liberia, Myanmar, and America, goddamnit.
Wine and liquor in the U.S. generally comes in metric sizes, but many (if not most) people still ask for a fifth (750 ml) or a half gallon (1.75 l).
I may be reading this wrong, but are you saying all SI units are metric or are fully commensurate with metric at a fundamental level?