(Although, technically, kilograms are supposed to be a unit of mass, not a unit of weight, so that kilogram bathroom scale won’t read accurately if I use it to weigh myself on the moon.)
That’s another great thing about the metric system - if you’re cycling or jogging, kilometres mount up much faster than miles 
Response to Curious_Georgie
The dumbest farm measure has to be the acre.
An acre = 43,560 square feet. (Gee that’s an easy conversion to remember - NOT !!!)
The number 43, 560 isn’t even a perfect square. It is a “convenient” 208.7103… foot by 208.7103… foot plot of land.
The standard was determined by the amount of land a farmer could plow in one day. Now that’s something that can be easily reproducible. Don’t they have that farmer and his plow in Paris right next to the platinum standard meter bar?
tracer: My nifty digital bathroom scale has a similar switch; however, it’s to select from kilograms, pounds, or stones.
Monty, you’re in California and you have a scale that measures in stone?!?
Actually, the acre, while being a dumb number of square feet, isn’t quite as ridiculous as all that. While a square 208.7103 feet to a side is pretty stupid, an acre is also precisely one rod* on a half mile (i.e., 16.5’ by 2640’). This makes it pretty easy to survey by the acre if your land is already divied up by the mile, half mile, quarter mile, or what have you. Acres are also 160 square rods, or 10 square chains, which aren’t nearly as silly numbers as 43,560 is.
Note: the above is in no way intended to suggest that hectares aren’t easier to work with than acres, but just to point out that the number of square feet in an acre is actually related to common (or used to be common) units of linear measurement.
Sunspace: Yep! I got it from the Army and Air Force Exchange Service.
Monty or Sunspace: So, is the stone a unit of mass or a unit of weight? (I.e. is one stone equal to 14 pounds, or does one stone weigh 14 pounds?) I’ve heard my dad jokingly refer to the “furlong-stone-fortnight” system of engineering units, so I wanted to be sure.
Gorsnak: So, then, it’s 4 rods to the chain, and 10 chains to the furlong, right? Which would mean an acre is 1/10 of a square furlong, or the area of a rectangle that was one chain wide by one furlong long.
One stone is equal to 14 pounds, but pounds are non-descriptive aren’t defintely either mass or weight units (that’s why some people prefer the terms pounds-mass and pounds-force).
Stone is only ever used to measure someones weight nowdays.
Q. How can the U.S. be metricized?
A. At gunpoint.
You’ll take my imperial rule from my cold dead hands!!
I know how we can get the metric system to catch on!
Okay, first, we’ll have to pass the NIST’s proposed amendment to the Federal Fair Packaging and Labeling Act, to allow manufacturers to label their products with metric-only units if they so choose.
But that’s only the first step.
You know how American consumers think that anything French is ritzy and sexy, like French wine and Paris fashions? Well, with American manufacturers no longer required to label their packages in ounces and pounds, they can package products in such a way that they look like they’re imported from France, when they really aren’t! (They can be packaged in Paris, Texas for added Frenchiness.) These products will be amazingly popular because people will think they’re posh French stuff, but in order to know how much they’re getting, they’ll have to read the net weight in grams or the volume in milliliters. The gullibility of the American consumer will be our salvation!
Yup, that’s all correct. It’s my understanding that rods and chains were originally primarily surveying units, i.e., there were actual chains that were 66’ long that were used to measure out land.
Depends on your reference point. Since I said it, you are
I believe that law was passed back when everyone was saying that Japan was kicking our ass. The belief was that we had to take measures (pun not intended) to be more competitive, which included converting to the metric system. So much for such nonesense, we didn’t convert and Japan has been in a 10 year funk. 
How does the U.S. convert to metric?
[ul]
[sup]Over my dead body[/sup][/ul]
No – the great big let’s-all-go-metric U.S. Federal law that everybody remembers, and which resulted in road signs being printed in both miles and kilometers, was the Metric Conversion Act of 1975. The whole Japan’s-economy-is-whipping-our-butts panic happened in the late 1980s.
The U.S. Federal Omnibus Trade and Competitiveness Act of 1988 did have some pro-metric sections to it, but these were largely invisible to the man-on-the-street.
<Men In Black> Your proposition is acceptable. </Men In Black>
I remember some of those traffic signs form that abortive attempt to go metric. 25 mph = 40 kph. Very nice. It was when they proposed that the freeway speed limit (the speed Nazis were in charge) would be 88 kph that I lost it.
I don’t think we’re going metric anytime soon. Too much cost, too little benefit.
That is pretty stupid. They should just round it off to the nearest 5 km/h, like they do in other metric-speaking countries. One road I drove on in Mexico was labelled as having a speed limit of 90 km/h, and that was so close to 55 mph as to not make any difference.
Actually though, an acre is exactly 1/640th of a square mile, so it makes some sense that way. I’m guessing this is why you always hear of “the back 40”, or why it was proposed to grant each of the freed slave families “40 acrers and a mule”. 40, 80, 160, 320, all these acreages neatly divide a square mile of land, so they were often used in parcelling out farms. Judging by my own family’s genealogical information, farm land was often sold or leased in such amounts.
So, that means there are 6400 square chains to the square mile, then. That’s actually a pretty decent round number – a square 80 chains on a side would encompass exactly one square mile.
Assuming we’re talking about Gunter’s chains here (which are 4 rods or 66 feet long), and not Ramden’s chains (which are 100 feet long).