April 21, 2010 5:11 PM   Subscribe

Give me some real-world benchmarks so I can understand the metric system.

Hey, guy born in the USA here. I'd like to use the metric system more, because I get how much more logical a base-10 measurement system is than one based on what a bunch of kings decided was normative a half millennium ago. Here's the problem: for 21 years, I've been surrounded by Imperial units every day and, though my sense of distances and degrees isn't great, I have gotten a sense of how far 100 yards is, and how cold 50 degrees Fahrenheight is and how fast 60 miles an hour is, etc.

Can you tell me any standard objects I experience in my day-to-day life that are equal to so many meters or weigh so many kilograms or go so many KPH? What Celsius temperatures are a cool and a warm day? How can I learn gradually to have an innate sense what metric units equal?
posted by l33tpolicywonk to Science & Nature (43 answers total) 27 users marked this as a favorite
Best answer: O degrees celsius = chilly
5 – 10 degrees = light cardigan
20 degrees = happy
30 degrees = sit in front of the pool

1 metre is roughly the distance from your hip to your foot

100 km/h = 60 miles an hour (that's not too hard to remember).
50 km/h = city driving
posted by fantasticninety at 5:14 PM on April 21, 2010

20 deg C is roughly room temperature. You can always use Google to convert units.

0C is freezing. 100C is boiling. -40 is -40.

100 km is about an hour driving on the highway (most Canadian highways have a 100 km/h speed limit). This is about 62 mph.

A carton of milk (a half gallon I guess) is just under 2L. 1.89L to be exact.

A yard is really close to a meter - a yard is .91m, so doing a straight conversion is less than 10% off.

A kilo is about half a pound - 454g in a pound to be exact.

Which is why you see everything in Canada in odd multiples of units - 454g packages, milk in 1.89L cartons, etc. They're really just imperial amounts.
posted by GuyZero at 5:16 PM on April 21, 2010

Best answer: A quart of milk is about a liter and has a mass of 1 Kilogram.
posted by bonobothegreat at 5:21 PM on April 21, 2010

A kilo is about half a pound - 454g in a pound to be exact.

Wait, I'm confused. Isn't a kilo a kilogram--1000 grams? I always thought a kilo was about 2.5 pounds.
posted by not that girl at 5:23 PM on April 21, 2010

Guyzero means a pound is about half a kilo.
posted by bonobothegreat at 5:26 PM on April 21, 2010

Best answer: The best cheat sheet I found for this that really helped me get a grasp on Celsius: XKCD: Converting to Metric. Embedded below:

posted by thebabelfish at 5:27 PM on April 21, 2010 [4 favorites]

Best answer: One gram is about the weight of one raisin or one paperclip.
posted by Houstonian at 5:27 PM on April 21, 2010

A kilo is 2.2 pounds.
An inch is 25.4 millimeters.
A meter is 39.4 inches.
A kilometer is about 0.63 miles. (So 100 km/h is 63 mph.)
posted by Chocolate Pickle at 5:27 PM on April 21, 2010

454g in a pound and the other thing I sad was backwards, yeah. A pound is about half a kilo.
posted by GuyZero at 5:27 PM on April 21, 2010

In Nineteen Eighty Four Orwell described a half litre of beer as too little and a full litre as too much.
posted by Fiery Jack at 5:28 PM on April 21, 2010 [1 favorite]

Whatever thing you use to check the weather - for me, that's the google desktop for a quick check, for instance - switch it to metric units. Manual thermometer? Tape off the F side. It's taking me time, but I'm slowly metricizing myself to temperature. But human body temperature is 'standard normal' at 37. No fraction!

Small measurements were always easy for me, for some reason. Measure a bunch of things - it seems easier to think of something as 'about four centimeters' than whatever partial inches they are. Your hip to the ground might not be a meter; I'm 155 cm and I always have to think about that in inches when someone asks me. I'm lucky to work in a hospital with a metric scale, so I can tell you my weight in kilos. If you have a bathroom scale, there may be a setting to switch it (digital) or tape off the lbs (manual.)

Volumes, weights? They're on most pre-packaged goods, although I'm pretty sure I can't ask for deli meat in grams, so I'm not sure that's avoidable. Recipes in the US are for volume, not weight, so if you really want to switch, you need a scale and some European cookbooks.

I can't measure distance in either, so I don't bother. Speed falls under the 'no one else is changing' problem, so, again, no reason to relearn speeds for driving.
posted by cobaltnine at 5:30 PM on April 21, 2010

Canadian here. These are my rough conversions/benchmarks. Most of my conversions are the other way round trying to remember what my US relatives are talking about.

1 kilo=1 kilogram=1000 grams = 2.2 pounds, so roughly a kilo = 2 lbs, and 1 pound roughly = a half kilo
2.5 cm = inch; 30 cm = 1 ft.
20 degrees C = room temp.
-40 F = -40 C
freezing = 0 C
metre = yard (usually close enough)
60 mph = 100 km per hr.
posted by kch at 5:32 PM on April 21, 2010 [2 favorites]

A litre is almost exactly a kilogram. As in, it used to be defined as such.

A kilometre is 5/8ths of a mile, or at least close enough to such. So if you need to go from miles -> km, the easiest way is: "add half, add a tenth". So 72 miles = 72 + 36 + 7.2 = 115.2 or so km. Online conversion gives me 115.8.
posted by Lemurrhea at 5:36 PM on April 21, 2010 [1 favorite]

10 yards is 9 meters, 10 feet is 3 meters.
My pinky fingernail is 1 cm.
1 hectare is 10000 m2, slightly less than a city block, and it's pronounced heck-tair.
Can of Coke is about 1/3 a liter (355 mL).
1 tsp is 5 mL, 1 Tbsp is 15 mL.
1 cup is about 250 mL.
posted by infinitewindow at 5:37 PM on April 21, 2010

Millimeter = width of fingernail.
Centimeter = width of small finger/black key on a keyboard.

Convert your height/weight into kg/meters, and then convert a few such measurements you're likely to use again, the way people in the US use certain benchmarks: 5 feet, 6 feet, 100 lbs, 200 lbs. When you want to see what the temperature is, use only celsius so you can get a sense of what it feels like. All of this is so you can get a good sense of the anchor points; after you've mastered those, you can start going into more detail: guessing others' heights in meters, speeds in KPH, and start ignoring the old imperial way bit-by-bit.
posted by blazingunicorn at 5:37 PM on April 21, 2010

For volume measurements you'll sometimes see cubic centimetres (cc) and millilitres (mL).

1 cc=1mL

Five millilitres is a teaspoonful.
posted by Tapioca at 5:38 PM on April 21, 2010

An couple of old mnemonics, from the days of the UK's first half-hearted attempts at conversion to metric back in the 60's / 70's:

"A metre measures 3 foot 3,
It's longer than a yard, you see."

"Two and a quarter pounds of jam,
Weighs about a kilogram."

That second one's not quite right; 1lb ~ 2.20kg, and it's sometimes easier to figure in fifths rather than quarters.

(Really, my only reason for posting those is the hope they get stuck in some other poor bugger's head for as long as they've been stuck in mine ;-)
posted by Pinback at 5:39 PM on April 21, 2010 [2 favorites]

110 yard is almost exactly a hundred meters

an inch = 2.54cm (two and a half is close enough for any thing I need before I can get to a calculator).

A kilometer is almost (but not quiet) two-thirds of a mile. 100 kph is just under 65 mph, not quiet speeding on rural interstates.

68f = 20c (a perfect day) 5degrees change in Celsius is 9 degrees in Fahrenheit (1.8 per degree).
posted by Some1 at 5:44 PM on April 21, 2010

I always remember that 5 degrees Fahrenheit is -15 degrees Celsius from looking at sleeping bag ratings...

either way... its cold.
posted by Nanukthedog at 5:58 PM on April 21, 2010

Best answer: 10 km/h = parking lot speed
40 km/h = residential streets speed
60 km/h = city speed
80 km/h = just at the edge of suburbs speed
100 km/h = posted highway speed
120 km/h = what most people usually drive highway speed
150 km/h = you lose your license speed
posted by tksh at 6:00 PM on April 21, 2010 [1 favorite]

I was raised on metric, and living in the US.

You can give up on miles vs. km. They're too big for you to be able to reference anything. I work with miles because the other units I relate those are miles-per-gallon and miles-per-hour. So I just use miles, and that's it... it's not like I had an intuitive notion of the length of a kilometer anyways... If I need to convert for some reason, I do the math. The only mental reference I have for km/h is that 110km/h is legal highway speed. Slower speeds for some reason are in m/s (10m/s is an olympic 100m racer, 8m/s is running, 6m/s is jogging, 1m/s is walking)

For Celsius - 0 is freeze and 100 is boiling (that's how the scale is defined, but those are also good intuitive benchmarks). Comfortable indoor temperature is in the low 20s, body temperature is 36-37.
"Hot" and "Cold" day are very subjective. Somewhere tropical/subtropical where people don't have indoor heating, 15C is very cold (It's mild if you're just walking outside, but try spending a whole weekend at 60F wearing a t-shirt). On the other hand, 10C is probably t-shirt weather in northern climates.
Outdoor temperature calibration is very subjective, and in my case, I just have two separate units in my head, Celsius, which measures temperature in Brazil (where 15C is freaking cold), and Fahrenheit, which measures temperature in Seattle (where 60F is nice). If someone tells me the temperature in Seattle in Celsius, I have to convert to Fahrenheit to make sense of it, and same thing if I see a Fahrenheit temperature for Sao Paulo.

a meter is roughly a yard (3 feet), which is a step in a normal stride. When dealing with large numbers (like mountain heights), it's just easier to multiply/divide by 3 to go between meters and feet. With medium sizes, funny enough, my "reference size" for metric is 30cm (very close to a foot), because that's the usual size rulers come in. For smaller sizes, it's 1cm (it's about the width of a fingernail, but I kind of have the size ingrained in my head), half cm (which I have somewhat "independently" from the 1cm measure... it's roughly a pencil's diameter), 1mm (a credit-card width). Measures between 1mm and 1cm are mostly by interpolation (I estimate how much of a centimeter/half-centimeter that thing I'm looking at seems to take). 10cm is slightly smaller than a CD. Anything between 10cm and 30cm or 30cm and 1m is by proportion as well.

A liter is close to a quart (two pints), and a pound is close to half kilo (by close I mean within 10%), these are easy (again, just doing the math works). So, useful references - a pint (beer) glass fits about half a liter, a coke can fits 350ml.
posted by qvantamon at 6:05 PM on April 21, 2010

if it's not obvious, by "width of a fingernail" I meant side-to-side, while for "width of a credit card" I meant the thickness.
posted by qvantamon at 6:18 PM on April 21, 2010

Best answer: 1ml=1cc
the neat part:
1 gram= 1cc of water at 4C (which is the temperature where water is at its densest)

also, you might try this art trick: measure all different parts of your body in metric; tip of thumb to first knuckle, width of closed fist, elbow to tip of middle finger, etc....then you've always got a metric ruler with you...
posted by sexyrobot at 6:37 PM on April 21, 2010

xkcd is an excellent comic, who just happens to have what you're looking for.

Do peruse the other comics. There is some hysterical stuff in there!
posted by wwartorff at 6:49 PM on April 21, 2010

Best answer: Tall people are 2 meters tall.
posted by chicago2penn at 7:12 PM on April 21, 2010

Best answer: Tall people weigh 100kg.
posted by kjs4 at 7:18 PM on April 21, 2010

Grew up abroad to parents from the US, so I had to make the transition backwards. Still have trouble with imperial units.

In Europe and China they sell juice and milk in this "brick-like" Tetrapack boxes that are one liter in volume. If you square a box of milk/juice, you get a cube 10 cm on a side. See one once and it's hard to forget.

If you pick up a box of milk or apple juice, it's about one kilogram. A box of water would be exactly 1 kg. Grams are too small for me to guesstimate, so I just use fractions of kilograms, as in "how many of these would make one juice box?".

When driving along a flat or slightly concave road out in the country, you can see about a kilometer down the road. A mile is more than twice as long and generally impossible to make out. Meters are about the same as yards; a basketball player is 2m or above. Most people are between 1m (kids) and 2m.

Temperature in degrees Centigrade is easy to think of in lots of 10: 0℃ is freezing, 10℃ is cold, 20℃ is normal/cool, 30℃ is hot, and 40℃ is record-setting hot.

I remember in elementary school we spent a lot of time with diagrams of staircases like this with the different units on them. To me as a visual thinker they helped a lot.
posted by msittig at 7:32 PM on April 21, 2010

A nickel weighs exactly 5 grams.
posted by yarmond at 7:48 PM on April 21, 2010

A kilometer is 5/8 of a mile. A mile is 8 furlongs. Useless to most, but if you are in a city where the city block is 1/8 of a mile (1 furlong), it is easy to reckon what a km is. 5 blocks.

As others have said, for water-based liquids, 1cc = 1 gm = 1ml for estimation purposes. So 1000 L is 1000 grams is 1 kilo is 1L. So a 2L bottle of soda (a universal if ever there was one) is 2kg.

For estimation purposes, a quart is a liter, a yard is a meter and 2 inches is 5cm. A toothpick is about a mm thick. The standard Sharpie is about 1cm thick.

A gram is about the smallest weight that you can "feel."
posted by gjc at 8:59 PM on April 21, 2010

One gram is about the weight of one raisin or one paperclip.

Technically, one gram is exactly the weight of one cubic centimeter of distilled water.
(That's what they said in school).
posted by ovvl at 9:10 PM on April 21, 2010

American, living in Europe, here. My first visit to Germany, I learned that 160 KPH is almost exactly 100 MPH. (99.41... according to Google)

Was picked up by driver for company I was visiting and rode in the front seat of BMW 7. Saw that we were traveling about 160 KPH and asked the (also American) driver how fast that was in miles. First answer was "you don't really want to know." When I got the real answer, it stuck with me for some reason.

I live in Germany now and routinely go 160 - 180 KPH (and think of it as such) on the autobahn in favorable conditions - just a learning process. Of course, really have to watch myself when driving in the US, especially on open highway.
posted by Expat at 9:33 PM on April 21, 2010

Best answer: The temperature mnemonic I've used since grade school:

30 is hot
20 is nice
10 is chilly
0 is ice.
posted by KathrynT at 10:47 PM on April 21, 2010 [1 favorite]

An average adult male would be about 80 kg.
A big one would be 100 kg.
A gridiron player would be 120kg plus.

Six feet is 183 cm.

A standard glass of wine is 100 mls. A standard bottle of wine is 750 mls.

A standard (european) beer is 330 mls, most cans are a bit larger at 375 mls.

Australia went metric about forty years ago, before I was born, but I still know my height in feet and inches.
posted by wilful at 11:41 PM on April 21, 2010

Scottish-born Canadian here, so I've lived in two places confused about their units: officially metric, but kinda not. Style tip: use lower-case l for 'litres'. Uppercase is a weird American thing that the rest of the world will look at you funny for using.

You know you've got it when you stop converting.
posted by scruss at 5:00 AM on April 22, 2010

not quite what you're looking for, but
when I was learning metric, I "memorized" these and extrapolated for numbers in between. I still do when I get confused.
posted by segatakai at 5:31 AM on April 22, 2010 [1 favorite]

I feel like people are making temperature too hard. A couple of years ago, I decided to make the move to metric in my head, and found it was pretty easy.

The basic principle is that 18 fahrenheit degrees equal 10 celsius degrees (the 9/5 thing is too confusing for me). This leads to:

First, you know your base: 0c = 32f [COLD]
Next, it's easy to remember that 10c = 50f [COOL]
It's also easy to remember that 20c = 68f [NORMAL], which is room temperature
For 30c, I just remember to reverse 68 to get 30c = 86f [WARM]
And my last benchmark is hot for Oregon: 40c = 104f [HOT]

I only really need to remember five points, and only 30c and 40c are trickyish. For getting at the non-ten celsius degrees, I just remember that 1c is roughly 2f. So, if it's 84f outside, I know to subtract 1c from 30c to get 29c. (And I mentally compensate for the 9/5 thing, so I know 77f is 25c.)

I don't know if I've explained this very well, but this is the method I've used for the past two years to think in celsius, and it works great. I really do think in celsius now, and find that I actually prefer it. It makes more sense to me.
posted by jdroth at 7:00 AM on April 22, 2010

30cm is around a foot (the length of a ruler)
4 inches is about 10cm (the length of a knitting gauge)
posted by Gor-ella at 7:16 AM on April 22, 2010

There are 28 grams in an ounce....don't ask.
posted by bonobothegreat at 7:18 AM on April 22, 2010

Technically, one gram is exactly the weight of one cubic centimeter of distilled water.

I came to clarify this as well. Someone else said up thread that 1 litre = 1 kilogram. This is true, if you are talking about water, (and close enough when talking about liquids that are mostly water, usually), but one is a measure of volume and the other is mass, so you can't make that assumption for X liquid.
posted by utsutsu at 7:43 AM on April 22, 2010

I'm going to piggyback on this question, because what the hell. I'm pretty comfortable with metric in general, but get turned around in the kitchen, because in the US, we use mostly volume-based measurements—cup, tablespoon, etc—and some customary measurements like pinch or dash that may be defined but are intuitively understandable.

AFAICT, metric kitchen measurements are all by weight—50 g diced carrots or whatever. Aside from the fact that these measurements always strike me as incredibly fussy, I don't have a handle on what 50 g of carrots looks like. Any rules of thumb here?
posted by adamrice at 7:47 AM on April 22, 2010

For baking, in approximate, good-enough terms:

Volume measures:
5mL is a teaspoon
15 mL is a tablespoon
30 mL is an ounce (fluid)
125 mL is 1/2 cup (4 oz)
250 mL is 1 cup (8oz)
500 mL is 2 cups, 1/2 a quart or a US pint
1000mL, 1 L is a US quart
4L is a US gallon
20L is 5 US gallons, the size of a plastic food service pail you would find at restaurant supply stores.

30 L is roughly a cubic foot
3/4 cubic meter is 1 cubic yard (useful for landscaping)
1000L, 1 cubic metre is a bit more than 250 galons.

30 g is an ounce (avdp)
125 g is about 1/4 lb
250 (really 225) g is about 1/2 lb
500 (really 450) g is a scootch more than a pound (about two ounces more)

35 kg is about a bushel.

Another handy unit:

2 acres is a bit less than 1 hectare (2.5 is very close)
posted by bonehead at 8:32 AM on April 22, 2010

Incidentally, when I'm scaling a recipe, I'll often convert teaspoons, tablespoons and ounces using the 5, 15, 30 rules, do the calculation then convert back to Imperial. It's way, way easier than figuring out fractional teaspoons.
posted by bonehead at 8:34 AM on April 22, 2010

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