Metric for ‘Mericans: How to Talk to the Rest of the World

Think you can communicate with non-Americans effectively?  Maybe.  Perhaps you speak a bit of Spanish, French or German… but do you speak metric?  In this piece, I want to convince you that if you’re not yet fluent in metric units that you really should be, and that I’ve got a way to make “talking metric” pretty quick and painless.

Americans have this reputation that when we travel the world, we expect people to speak English and, when they don’t for some reason, we just repeat whatever we said, but more slowly and loudly.  It’s a funny image and we’re fun to pick on, but in truth I travel a lot outside of the country and I’ve never seen an American do that.  I’m not saying that it never happens, just that maybe it’s something that happened in the 40’s at the end of WW II or something like that.  When I know I’m going to be somewhere out of the country, I get a phrasebook and try to learn somewhere between 20 and 40 phrases, as well as finding out beforehand where there’s a hotel whose staff speaks English, and all’s been well in my experience.

One place where I do find that Americans fail to connect with non-Americans, however, is in units — miles, inches, acres, pounds and the like.  When I first started teaching outside the US in the early 80’s, I told stories and answered questions in a manner that employed America’s semi-Imperial units, as in

“I just installed Paradox [a database program that shipped with a pile of floppies and a few hefty manuals] on my laptop and, oddly enough, although the box that it came in weighs 29 pounds, the laptop did not gain any weight!”

(That passed for techie humor in 1988, in case you’re wondering.)   Even out of the country, the line got a smile, but there was a slight pause in some places, particularly among younger folks.  Then, about 15 years ago, I was sitting with some attendees from South Africa at lunch, and I described a factory’s size in acres.  They looked at me sheepishly and explained that they had no idea what I was talking about.  Since then, I’ve met plenty of folks whose understanding of American units (I’m not calling them “English” because, again, the Imperial units are a trifle different) is anywhere from sketchy to “um, how many guineas are in one of those ‘miles’ you keep taking about?'”  I’m not kidding about this — metric is so ubiquitous outside of the US that I have a good friend who hasn’t a clue what I mean when I say that a restaurant’s only about three miles away, and she lives here, so I’ve gotten a bit more adept at saying, “um, I mean five kilometers,” and then all is well.

Similarly, I had dinner with a number of folks from a security-related company a while back, and was seated next to the organization’s boss, a man who’d lived all of his life in metrified countries in Europe.  We had a great conversation and at the end of it, he remarked how nice it was to have spoken with “an American who could speak metric — it hurts my head to have to convert when talking to most Yanks.”

Eventually, it dawned on me that it’s not only polite to be able to speak metric, it’s essential if you want much of your non-American audience, customers or (maybe) airline seatmates to understand you.  Furthermore, that will be more and more true as time goes on, as people from places that have gone metric only in the past few decades may be good with American units now, but may NOT be as subsequent generations grow up in an all-metric world.  For example, Canada went metric in the mid-70s, and my Canadian friends tend to be old farts like me, so they’re fine with either set of units.  But I wouldn’t be surprised if many adult Canadians in, say, 2020 might be a bit unsure when hearing American units.

Okay, let’s say that you’re still reading, may be at least partially convinced, but haven’t done much metric because of all of those ugly conversion formulas.  Who wants to have to whip out a calculator every time you want to figure out what it means if the beach is 32 degrees Celsius or if you want to know how many kilometers are in your 20-mile commute daily?  Here’s how.

The barrier to “metric fluency” is, I think, that formulas are too darned complex and (usually) unnecessarily precise.  32 degrees Celsius is 89.6 degrees Farenheit, and 20 miles is 32.2 kilometers, if you do it the calculator way.  But let’s re-examine the REAL essence of the two imaginary conversation snippets wherein you’d need or want to swing both ways.

First, the beach.  You’re getting ready to drive out to the sea from some Brazilian town and you hear on the radio that it’s 32 degrees at the beach.  Do you really care whether it’s 85 degrees or 94 degrees Fahrenheit?  No, of course not — you just need to know  whether to bring your wool coat or a t-shirt.  To that end, let me quote how a Celsius-fluent friend explained it to me about 25 years ago:

  • At zero degrees C [32F], it’s cold.
  • At ten degrees C [50F], you need a jacket.
  • At twenty degrees C [68F], it’s room temperature — comfortable.
  • At thirty degrees C [86F], it’s hot.
  • At forty degrees C [104F], it’s REALLY hot.

Simple and easy to remember.

Then consider the comment about your commute.  You’re in some city in Turkey chatting with a new acquaintance about life and they say that they bike 15 minutes a day to work.  You reply that biking would be pretty impractical given your commute of 20 miles, but want to say it in kilometers (abbreviated “km,” and colloquially called “klicks” in some countries).  To covert miles to kilometers, multiply the miles by 1.609344 … ugh.  Again, think about what you’re trying to convey — a long, not-conveniently-biked distance.  Why bother with a precise calculation of 20 x 1.609344 when you’re probably not all that sure of the distance of your commute in the first place? For example, I drive from my home in Virginia Beach to Norfolk International Airport (“we’re international because we run one flight a day to Toronto”) fairly often, and have for the past 13 years or so, but I couldn’t tell you how far the trip is in miles.  I’d estimated it at about 17 miles, but I just looked it up and found that it’s actually 24.6 miles, a 45% error.  I’ve mentioned that 17 mile guess to dozens of locals in the past 13 years and no one’s ever thought it wrong, nor have they  questioned it in the least — for the purposes of the conversation, it was a perfectly fine number.

So here’s how to convert miles to kilometers:  multipy them by two.  Don’t tell your new friend that you have a 20 mile commute, and don’t whip out a calculator and figure out that you have a 32 km commute — just double “20” and tell him or her that you commute about 40 km every day.  Nobody will be inconvenienced, and your new friend will get an idea of the distance immediately.  Everybody can double numbers in their head.  But what if feel that you need a bit more accuracy and you capable of a bit of mental gymnastics?  Then multiply it by 1.5.  The mental way to do that is halve the number, then add it to itself.  In the case of the 20 mile commute, half the number is 10 and then add it to the original number (20) to get your estimate of 30.  Only a bit harder, and yields a closer estimate.

So here’s how to do those estimated conversions.


1) Temperature:

In addition to the five numbers above, there are a few others worth knowing:

  • Boiling water:  212F is 100C.  So definitely do NOT get in a bath where the water is 98 degrees C (208F)!
  • Comfortable hot water:  most of us like a hot tub no warmer than 104F which, recall, is 40C.  If you like a 120F shower, that’s 49C.  Don’t even think of getting near water that’s hotter than that, unless you’re very careful.
  • Body temperature:  the “normal” 98.6F is 37 degrees in C. Notice, in fact, that the C value comes out to an even integer, and the F value doesn’t.  I’ve heard a story that the original folks who measured body temperature after the invention of the thermometer did it in C, measuring an average value that they rounded to 37 degrees.  People in Fahrenheit-using areas just ran 37C through the standard “9C=5(F-32)” and you get exactly 98.6 degrees F.  Instead of rounding to 99 — which would have been easier to remember and every bit as useful in everyday life — they gave us that “.6.”
  • REALLY bloody cold:  minus 40 degrees F in Celsius is… minus 40.  That’s the only pair of C and F temperatures that are the same.

2) Distances and lengths:

As I’ve already argued, kilometers = miles doubled.  So run it the other way to convert from kilometers — just halve the number of km to get an estimate of miles.

Convert yards to meters and vice versa:  American yards = metric meters.  Okay, it’s not exactly true.  A yard is 36 inches, a meter is 39.37 inches, but in most cases the difference won’t matter.

Instead of saying, “he fell eight feet to the ground,” convert feet to yards in your head — divide by three, recall — and say, “he fell two and half meters.”  (Keep things either to integers or integers and a half.  We never say, “my tomato plants are one and 2/3 feet high” — we’d say a foot, a foot and a half, or two feet.)  Again, nobody cares whether he fell 2.5, 2.6 or 3 meters… in any case, it’s a significant drop.

Convert Inches to centimeters: multiply by 2.   For example, a 24″ (61 cm) window is close enough to 48 cm wide. Need better accuracy?  Well, the correct value is that 2.54 cm equals 1 inch.

More accurate but a little harder:  If you’re comfortable with taking a number, halving it and doubling it and adding those together, you’ll get a better estimate.  For example, if a window is 24 inches wide, you might convert that to centimeters by doubling it (48) and halving it (12) and then adding 48 and 12 together to make it 60 cm.

Another approach is to divide the inches by 4 and then put an extra 0 on the end.  For example, 24 divided by four is 6, then add a zero to the right and you get 60 cm estimated.  For example, to express how amazingly large your 60″ diagonal HDTV is, take the 60 inches and divide them by 4 to get 15.  Then add a zero to the right and you’ve estimated 150 centimeters. (Actual value is 152.4.)  Whoever you’re talking to will be properly impressed.

Centimeters to Inches: convert centimeters to inches by halving them, reversing the above process, so 70 cm becomes 35 inches.  For a closer estimate, multiply by four and drop a decimal point — 70 cm x 4 is 280, then drop the rightmost digit and get 28 inches.

3) Area

Convert square feet to square meters:  divide by ten.  (The real divisor is 9.3.)  Thus, if your new McMansion is 4000 square feet, that won’t compute when talking to a guy from Tokyo who you’ve just met on the plane.  Say your new house is 400 square meters and he’ll get it.  (Houses built in the US in the past 20 or so years seem insanely large compared to what most people like in other countries.  A 150 square meter — 1600 square feet — house is considered “big” in much of the world that I’ve been to.)

Convert square meters to square feet:  the reverse — just add a zero to the end of the square meter value and you’re there.  A 110 square meter house is roughly 1100 square feet (1184 in reality).

Convert acres to hectares:  most of the world would describe the amount of land that their houses sit on not in acres but in “hectares,” an amount of space equal to 10,000 square meters.  One hectare is 2.47 acres.  Notice that the conversion factor of 2.47 (hectares to acres) is very close to the value for inches to centimeters (2.54), so just use the same formulas.

In other words, the rough way to convert acres to hectares is to divide acres by two. So, if you live on quarter-acre lot, it’d be .25 x 2 or one half hectare the rough way.

More accurate but a bit harder:  The closer way to convert acres to hectares is to multiply the acres by four, and then shift the decimal point one position to the left.  In the case of your quarter-acre lot, you’d multiple it by four (.25 acres x 4 = 1), then shift the decimal point one position to the left, changing “1” to “0.1”  .

Convert hectares to acres:  reverse as you do to go from inches to cm.

The easy way is to just double it, so for example 1.5 hectares becomes 3 acres. (It’s really 3.7.)

More accurate but a bit harder:  the closer but harder-to-do-in-your-head estimate runs like this: divide by 4, then shift the decimal place over to the left, adding a 0 to the end of the number if necessary.  Starting from that 1.5 hectare lot, then, we’d divide by 4 to get roughly .4, then shift it to the left to make the 0.4 into 4 acres.

That was ugly with the 1.5 example but gets easier with rough big numbers.  If someone tells you that she’s going shooting wildlife somewhere in Africa on a 1000 hectare park, divide 1000 by 4 to get 250, then add a zero and get roughly 2500 acres. (2471 is the closer answer and, again, who cares… do any of us really know the difference between a 2000 acre park and a 2500 acre park?  I sure don’t and in any case I wouldn’t want to have to mow it.)

4) Liquid Volumes

In metric, we talk about things like automotive fuel, oil, water, blood, wine, soda and the like in liters (“L”) and milliliters (“ml”).  There are 1000 ml in a liter.

Convert liters to quarts and quarts to liters:

A Liter is just a bit larger than a US quart — one liter equals 1.06 US quarts.  (I’m writing “US quarts” because UK quarts are 1.2 times the size of US quarts.)  So you know what we’re going to do… just estimate by making them the same:  one quart of milk is “equal enough” to one liter of milk, and a gallon of gas is about four liters of gas. (Remember, there are four quarts in a gallon.  And while I’m on the subject, most countries don’t call gasoline “gas,” so be careful.  More than one American has filled their tank with diesel in Europe mistakenly.)  Many beverages and food products retail in a bottle that’s about a pint and a half, but I’ll bet you already know that, as the ONE bit of metric that even we Americans know is the 750 ml bottle. (And, I guess, the two-liter soda bottle.)

Convert ounces to ml:  small amounts like this are always in ml.  An ounce is about 30 ml, a shot of alcohol is about 45ml, and a raindrop is about a half ml.  You can usually skip worrying about converting, though, as “shot” and “raindrop,” well, mean the same thing everywhere!

5) Weights

Convert pounds to kilos:  metric users express weight not in pounds but instead in “kilograms,” almost always said “kilos” and written “kg.”  One kilo equals 2.2 pounds, so just dividing pounds by two will give you a quick and not-too-inaccurate estimate of something’s weight in kilos.  For example, my car weighs 1880 pounds, so calling it about 940 kilos isn’t a terrible estimate, even though it’s really 852.  Although there IS at least one case where you’d want to be more accurate…


Does this always work?  Definitely not.  There are a few numbers that people use wherein they DO notice inaccuracy.  You know, like “how many fingers do you have?”  Despite the fact that “11” is only ten percent in error when enumerating most people’s fingers, you’ll get a very distinct reaction if you describe someone as having 11 fingers.  Here’s a few biggies.

1) Height, weight or other personal statistics.  “A yard equals a meter” is fine for most estimations, but say that someone who’s 6 feet tall (two yards) is two meters (6 feet, 6 inches), or that a guy who weighs 80 kilos (176 pounds) weighs 160 pounds will get a funny look or two.

2) Cooking amounts.  A kilogram of flour is 2.2 pounds, NOT 2 pounds… most recipes won’t come out very well if you’re not exact.  Time to get out the calculator, or a digital scale with an “english/metric” button.


Quickly summarizing, convert from American to metric like so:

  • Divide miles in half to get kilometers.
  • Don’t change yards at all, just call them meters.
  • Multiply inches by 2 to get centimeters.
  • Convert C to/from F with our example values: 0 is freezing, 10 is cool, 20 is comfortable, 30 is hot, 40 is really hot — hot tub hot — and don’t get into a shower hotter than about 48.
  • Divide square feet by ten to get square meters.
  • Divide acres by two to get hectares.
  • Quarts and liters are about the same.
  • An ounce is about 30 ml.
  • Divide pounds by two to get kilos.

I hope this has got you thinking a mite more comfortably in metric.  In a world of over 200 countries, there are only three and a half* nations that still use English/American units, so you know it’s just a matter of time before we’re entering a new year thinking that we’ve got to drop that five kilos we picked up after the holidays, worrying that our baby’s got a temperature of 39, and wondering if that new edition to the house can all fit in 50 square meters!

*I count the UK as one-half metric as they’ve been officially metric for quite some time, but most folks I talk to still talk miles, pounds, and such.  For example, many people in the UK still describe their weight as “twelve stone,” where a “stone” equals 14 pounds.  Talk to a Brit about his car and he’s likely to describe its engine displacement in liters, but then to describe its gas mileage in miles per gallon.


One thought on “Metric for ‘Mericans: How to Talk to the Rest of the World

  1. Cedric says:

    I like this explenation, it helps me as a metric person also to talk to americans 🙂 Well I got it somewhat down but when I lived in Illinois I still was the only person in the furniture store with a metric ruler even tough the sizes where written there in US 🙂

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