How can I learn to use metric in my everyday life?
August 17, 2005 4:20 PM   Subscribe

I want to Think Metric! I'm an American who wants to get on par with the rest of the world. What are ways I can start to mentally convert from inches, pounds, and Fahrenheit to centimeters, kilograms, and Celsius.

I've checked out some sites like Think Metric that give every day examples (a one story building is about three meters) , but find it hard to switch around the English equlivants (a builiding that size is about 10 feet, so three meters is ten feet, or ten feet is about three meters). What are some better ways I can mentally convert and use metric in my every day life?
posted by jazon to Grab Bag (22 answers total) 2 users marked this as a favorite
Best answer: Things became easier when I figured this stuff out:

1 sq. meter is about 10 square feet.

1 liter is a bit more than a quart, and 1 gallon is not quite 4 quarts.

1 pound is a little less than half a kilo, and a kilo is a bit more than 2 pounds.

1 dry ounce is about 30 grams.

A kilometer is a little over half mile.

A dime is one millimeter thick. One foot has 30 centimeters, so 10 cm is 4 inches.

As for temperatures, I just memorized it. 10 degrees C is a cool day, 20-25 is pleasantly warm, 30 degrees is quite warm, and 40 degrees is too hot to move away from the A/C.
posted by luneray at 4:36 PM on August 17, 2005

I meant that a gallon is not quite four liters.
posted by luneray at 4:36 PM on August 17, 2005

(F - 30) / 2 = C
(C x 2) + 30 = F

It's clearly not perfect but it's a good approximation for daily temps and easier to do in your head than the real formulas.
posted by smackfu at 4:50 PM on August 17, 2005

I've lived in the UK for almost two years and have just started learning Celsius recently. What I finally did was write a program that displays a thermometer with the current temperature in red in both Farenheit and Celsius, which is the first thing displayed on my computer each morning. Eventually you just start to learn it.
posted by grouse at 4:55 PM on August 17, 2005

Best answer: Don't mentally convert them, think of them as completely different measurement schemes. Metric isn't a conversion of American standards any more than German is a translation of English.

I mean, you don't pick up a two-liter soda bottle and wonder how much is in it, do you, or mentally translate it to about two quarts or about a half-gallon? It's just a two-liter bottle that's two liters big. Ditto the grams of fat in food you eat, or tools and sockets, and so on.

So just start using the metric system in your daily life when you can. Don't convert, just use. Measure your weight in kilos, not pounds, and your height in cm, and so on. You're going to find this really hard, probably, because almost all of the measurements you're presented with instead of measuring yourself will be in the American standard units.

If you really want to think metric, spend a vacation somewhere deeply metric where you won't have the crutch of American-standard measurements presented to you. The UK or Canada probably don't count here as you're likely to find substantial remnants of Imperial units, at least in informal usage among adults.
posted by ROU_Xenophobe at 4:56 PM on August 17, 2005

Best answer: Australia went metric in 1975. I was 13. I still find myself thinking in inches occasionally, but pints, pounds and Fahrenheit are pretty much replaced (except for tyre pressures - I still measure those in pounds per square inch, not kilopascals).

I think the key is just to use metric units whenever you can, and trust you'll get used to them. Pick one physical quantity at a time, and every time you find yourself needing to think about a measurement in that quantity, remind yourself of the metric equivalent. Once you've been doing that for a while, move on to the next quantity.

Start with using millimetres and kilometres instead of inches, feet and miles. Don't bother with centimetres; nobody in the civilized world does :) and don't use metres for measurements with better-than-one-metre precision. Yes, it is completely bizarre to think of a nine foot length of two-by-four as 2700mm of 50 by 100, but it will grow on you (the fact that you very rarely have to use fractional millimetres is a plus, and makes up for the ridiculous numbers of them you need for everything).

Remember that an inch is exactly 25.4 mm, by definition. Take that as the starting point for all your length conversions and you can't go wrong.

32 and 212 Fahrenheit are exactly 0 and 100 Celcius, also by definition.

For house sizes and land areas, think of ten square metres as a hundred square feet (it's actually 93, but whatever). Two and a half acres make a hectare. Ten miles is about sixteen k. A tonne (1000 kilograms, for some reason never referred to as a megagram) is near enough to a ton. A tonne of water occupies a cubic metre (to within 0.001% at 4 degrees Celcius).

Those should get you started. Enjoy the trip!

On preview: I think the advice just to use, not convert, is basically sound - but you will need to spend some time with conversions to get you started; just as you need to spend some time with translation when picking up a new language.

And if you want to do the immersion thing, come visit :)
posted by flabdablet at 5:16 PM on August 17, 2005

A litre of water weighs exactly a kilogram.
posted by uncanny hengeman at 5:28 PM on August 17, 2005

uncanny hengeman: "
A litre of water weighs exactly a kilogram.

And occupies exactly 1000 cubic centimeters, or a 10x10x10cm box.
posted by signal at 5:34 PM on August 17, 2005

And I'll put hengeman's and signal's great hints together, for...

one liter = 1000 milliliters (ml) = one kilogram = 1000 grams


one ml = one cubic centimeter (cc) = one gram

The metric system is beautifully simple once you get to know it.
posted by lambchop1 at 5:45 PM on August 17, 2005

I use the double-it-add-30, subtract-30-halve-it thing when explaining the weather in Oz to my mum in Florida. I was amazed at how quickly she went native. "It's 5oC" I say. She can't remember if that's hot or cold, until I say "5-10-it's about 40oF", and the penny drops.

If I need to convert kilos to pounds I double it and add 20%. For example, 5kg is (double 5 is 10 plus 1 is) 11lbs. Alternatively, add 10% then double it. So, 7kg is (double 7.7) about 15.4lbs.
posted by obiwanwasabi at 5:55 PM on August 17, 2005

Stop converting. Once you live metric for a short period it will sink right in. You could start easily with a few Celsius thermometers.
posted by caddis at 5:56 PM on August 17, 2005

I second ROU_Xenophobe--you should avoid conversion. It's like learning a new language--if you're translating from English, you'll never speak properly. Context is everything, so walk through stores and guess. You must see a four litre milk jug, a thirty centimetre ruler, and attach the objects to the measurements in your mind. You can extrapolate from there--how many milk jugs would fit in that aquarium--about ten? Forty litres. Comfortable in this room? 20 degrees Celsius. Ice cubes? Zero--that's easy. You will have new insights--the human comfort zone is not halfway between freezing and boiling, but near 20 percent, at the cool end.
posted by weapons-grade pandemonium at 5:57 PM on August 17, 2005

Use a temperature applet in C. Switch your bathroom scale to kilos. Etc.
posted by holgate at 6:31 PM on August 17, 2005

Just to reinforce what has been said already: find a way to convert at first (to get a handle on the scale of things) but try as soon as possible to think like a native. It's really like learning a new language ... except that it's easy to get stuck in the conversion trap.

Canada went metric when I was a young teenager; I am somewhat fluent in both systems. I worked as a physicist for many years, using only metric units for my work. Yet, when it comes to temperatures or distances in daily life, I can "guestimate" intuitively in English units but have to think hard (and sometimes do the mental conversion) to get the metric equivalent.

By comparison, I learned English as a second language, starting as a teenager. When I moved to an English city (Vancouver) I made an effort *not* to "convert" from French (i.e. translate). Now, I never need to translate from French to English .... but still do from English to metric :-)

Good luck!
posted by aroberge at 6:48 PM on August 17, 2005

Response by poster: Good stuff. I'll start with length and go from there. (And thanks for the tip, flabdablet, about using mm instead of cm).

My concern/worry/stumbling block (and motivation for this AskMe) was wanting to be metric while being surounded by imperial - the barber saying he'll take an inch off the top and me thinking 'Ah, 25 mm!' but hopefully I'll start taking on little bits and get more proficient over time.
posted by jazon at 6:50 PM on August 17, 2005

Holgate has a good one, I've installed Forcastfox which always shows the current temperature C on my browser's bottom bar. "Converting" doesn't work for me, I just have to treat them as separate.
posted by sohcahtoa at 7:28 PM on August 17, 2005

A litre of water weighs exactly a kilogram.
And occupies exactly 1000 cubic centimeters, or a 10x10x10cm box.

Well, that was the original intention, but the current reality is a bit more complicated.
posted by randomstriker at 8:55 PM on August 17, 2005

Regarding temperature conversions, I try to remember a few benchmarks. Everything else I just estimate in between

-40 F = -40 C (cold)
0 F = ~-18 C ("below zero" F < 18 c)br> 32 F = 0 C (water freezes)
50 F = 10 C (+/- 40)
72 F = 22 c (+/- 50)
82 F = ~28 C (reciprocals)
98.6 F = 37 C ("normal" body temperature)
104 F = 40 C (a pretty high fever)
140 F = 60 C (cooking on low)
212 F = 100 C (boiling water)
~400 F (392) = 200 C (baking)
posted by zachxman at 7:28 AM on August 18, 2005

Sometimes conversions are useful. If you only have one set of wrenches, you might want to remember that 5/16 inch is 8 mm, 7/16 inch is 11 mm, 1/2 inch is 13 mm, and 3/4 inch is 19 mm.

They are not exactly the same, but are within the tolerances that nuts & bolts are made to, and the wrenches are functionally interchangeable.
posted by Kirth Gerson at 8:18 AM on August 18, 2005

Some good advice here. It's certainly a great idea to try to think only in metric but as you rightly observe, this is hard to do when the people around you keep talking imperial at you. Take a long holiday in Europe! No but seriously:

8km = 5 miles, so for long distances the math isn't too bad. Otherwise go with the "1 km = a bit over half a mile" advice.

1 metre = a bit (three inches-ish) over a yard.

I'm not going to confuse you with capacity because I'm British and our pints (and hence also our quarts and gallons) are different from yours - 20fl oz to a pint rather than 16.

Temperature - you know, I just remember a few key points like 32F = 0C, 212F = 100C, human body temperature = 98F = 37C, "room temperature" = 70F / 21C and so on.

Another idea is to study a scientific subject, especially physics. That'll have you thinking metric in no time.
posted by Decani at 8:48 AM on August 18, 2005

I became familiar with day-to-day (not scientific) use of metric measurements only after lots of travel.

The problem with trying to use metric measurements out loud in the USA is that people will think you're trying too hard to be different or that you're a snob.

Still, I think the best way to relate to the world using SI is to know yourself in these units. How many centimeters tall are you? How many kilos do you weigh? How hot is it outside? How does that temperature feel?

Other than these nice facts, the metric system is disappointingly useless for day-to-day purposes here in the USA. Maybe you and your friends could start using it so that it could come up often?

In regards to terms used, I noticed that in Australia and NZ (at least, don't know about elsewhere) they refer to kilometers as "kays". I also find it easier to say "sennimeters".

Remember that when you go to metric countries, people there will be surprised that you know metric units! You'll gain points towards "Cool American" status (which isn't that hard to achieve, since they automatically assume we're all cretins anyway).

Have fun!
posted by redteam at 9:38 AM on August 18, 2005

randomstriker: "A litre of water ... occupies exactly 1000 cubic centimeters, or a 10x10x10cm box.
Well, that was the original intention, but the current reality is a bit more complicated.

Well, kilos might have gotten complicated, but the last time I checked, 1 L = 1000.000000000000000000 cm3
posted by signal at 9:53 PM on August 19, 2005

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