I myself never really had an intuitive grasp of weights and measures anyway, so when I decided I would work with metric where possible, I was more-or-less starting from scratch with metric. Perhaps it is ironic, then, that getting an intuitive sense of what these numbers mean has forced me to learn a lot more about the Imperial system, especially since it sometimes involves explaining myself.
Long distance isn’t much of an issue. I still can’t picture a mile in my head, and the fact that it’s 5,280 feet doesn’t help. Since in practical usage miles are usually given as ballpark figures, adding half again to get kilometers doesn’t risk losing much accuracy. Of course, it just becomes another number whose import I don’t really grasp, but it’s a start at least. In terms of speed:
50 km/h - residential
70 km/h - service roads
100 km/h - highways
110 km/h - interstate
130 km/h - only in West Texas
Yards are almost always given for approximate measures, and are so close to meters that you might as well think ‘meters’ when you hear ‘yards.’ In fact, in news reports about millitary incidents I notice that where some reports will say a soldier fired from fifty meters, another will say it was fifty yards. If someone wants help grasping the difference, I have heard that a meter is a yardstick plus a fresh piece of chalk.
I can generally remember how long a foot is, because it’s about the size of the average ruler. And that happens to be about 30 cm. So from that I’ve got a rough idea of what 10 cm looks like, but it’s easier to make guestimations in intervals of 12 cm, because that’s the diameter of a CD or DVD. 5 cm is the distance from the hole in a CD to its rim. I carry a small tailor’s style metric tape measure good to about 1.5m and measure things now and then to keep perspective. At home I have a larger tape measure good to about 8 meters.
I couldn’t pick up an object and tell you how many pounds or ounces it weighed. However, I do have a basis for ballparking it in metric, because I know how hard it is to lift a 2-liter bottle of pop, which is approximately 2 kilos – the design function that a liter of water weighs a kilo really helps make metric more intuitive here. I bought an electronic scale that measures up to 5 kilos with an accuracy out to a tenth of a gram. I find it maddening that recipes give volume specifications for dry weight. In home ec we were told we had to check to see if the amount of flour specified was sifted or unsifted, and you might have to go through another messy step to make sure you get the measurement right. Madness! Of course, a friend has advised me that the police consider a gram-weight scale to be drug paraphrenelia.
I generally understand the numbers on temperature in Farenheit, and that’s more trouble to rule-of-thumb. I have acquired a bell-style thermostat marked off exclusively in celsius, but I haven’t installed it because frankly I might as well go ahead and get a digital thermostat that can be switched to metric, because it would also be programable. Still, I keep the little metric Honeywell around as a knick-knack, because although it wasn’t hard to find, it was nonethless a rare bird. I will keep in mind Anne Neville’s little verse, though. That will help with the conversion.
As for liquid, I of course know what a gallon is because of milk. And I know what 2 liters is because of pop. I can approximately remember gallons to liters because 750 ml bottles of liquor are referred to as fifths (of a gallon). But I would never be able to estimate the volume of larger than a couple of gallons or three liters just by eyeballing it. So, liters are no more abstract for me at large volumes, but they have the advantage that I can suss out volume from estimated dimensions in centimeters or meters. Of course, you can also do so in Imperial. Ever tried it? A gallon is 231 cubic inches, a cubic foot is 7.48 gallons. A cubic yard is close enough to 200 gallons as to make no never mind, so your neighbor’s swimming pool should be an easy enough guestimate. Otherwise, fooey. Frankly, I don’t seriously believe anybody else can picture more than ten gallons in their head with any accuracy, so if they give you the stink eye for speaking in liters, that’s their hangup.
Not that I don’t have my own hangups. I hate to see a science or science fiction show set in the future using Imperial measures. The new Dr. Who does this all the time. They’re afraid the audience wouldn’t be able to get their heads around billions of kilometers, but billions of miles will make sense? Yes, ‘kilometers’ takes longer to say. That’s why we say ‘klicks’ instead.
I don’t bake much, so in most of the cooking I do I figure 240 ml is good enough for a cup, which is a fairly arbitrary measure. I’d prefer to make it 250 since that’s neatly divisible into a liter, but 240 is more subdivisible by half and a quarter. Cooking is an art, they say, whereas baking is a science, but you can’t tell me that a lot of wiggle room didn’t go into matching up arbitrary, unrelated and ungranular units like teaspoons, tablespoons and cups. What we need to know is what the actual thresholds are, what the real proportions are that the spoons are approximating – lemon juice to baking powder, for instance.
In trying to convert my word processing to metric, I discovered that you get odd numbers when moving things around, and can’t ever get the grid to snap to precise numbers of milimeters. Clearly when you set Word to metric, it’s still thinking in inches and only displaying the nearest milimeter. Plus, A4 is more expensive than Letter sized, and has to be special ordered. But the adjustable tray on my printer could accomodate it.
I also play roleplaying games, which are mostly done in Imperial measures. As far as I know, D&D is sold across the world with this nutty system built in. The actual conversion is actually straightforward, except where the arbitrary choices of weight meant to be convenient numbers in pounds can be awkward ones in kilos, even if you’re simplifying the conversion to 2 pounds per kilo. But at least the distances worth bothering with are generally in squares these days, and whether a 25mm or 1 inch square represents 5 feet across or 2 meters doesn’t matter in the game scale. I don’t bother converting D&D to metric (though I would if the players tempted me, by god – they’re lucky I don’t make them learn a new calendrics system and try to guess what the weather might be like on the ‘swordfall’ of ‘applemeet’), for science fiction games metric is a must. I can get behind a world in which humans extend their reach to new worlds only to meet an alien threat bent on their destruction. But if those humans are still ordering their lager by the pint, let the aliens have 'em.