Thanks Percy, you did outstanding work showing -40C equals -40F. But you are about a "day late and a dollar short". Rizzuto already answered. However, once again you show your work!!!! So you still get a big "thatta boy"!!!!!

regards - tom

Celia, you're welcome.

ann_nyc, glad it works for you.

Tom, I was afraid you'd ask how to go the other way. I think
P_M had a decent approach, i.e., substract 30 and divide by 2 (but I think if you add 2 to your answer you'll be almost spot on--without it the answer the approach gives appears to be 2 too low). 80 - 30 = 50 ÷ 2 = 25 (+ 2 = 27).

Steve

Guess I missed P_M's subtracting 30 and divide by 2. That's probably as easy as we're going to get it. P_M's going C to F of taking C multiple by 2 and adding 30 is also easiest. Think I'll use those two for everyday weather temp. Thanks P_M.

regards - tom

cary999

Gosh darn ,I did want those "Extra" credits :)

Here's how I do it:
http://metricconversioncharts.org

print it out and take it along when travelling; easy!

You are most welcome Tom. :-)

Well, so, as a Canadian I just feel compelled to weigh in here (in lbs not kg) :-))

I am, probably like Percy, one of those boomers that got stuck in the middle - we grew up learning lbs, miles, farenheit. We knew that as a teenage girl we should only weigh 125 lbs max, that driving with our friends down the highway should only be 60 mph - or well, Ok, we stretched that one a bit. And that we needed to be in bathing suits at 95 degrees, t-shirts & shorts at 80 degress, a jacket at 60 degress, a winter coat at 30 degrees, and at home watching TV at 40 below farenheit (yes, I'm from the prairies).

Then, suddenly this guy stands up & says, no wait, we should be on the metric & by golly we will not let any products into our country unless it is in grams not oz - and oh by the way it also has to be in French too.

So, as adults (or semi-adults maybe) we all tried very hard to learn the metric system. We cheered our kids on when they came home from school proudly displaying that they knew the metric system, but also secretly smiled when they talked about inches instead of cm - must have learned that too we thought!

But, Percy is right - we may have learned the metric system - or some parts of it, but we still use imperial measures in day-day things. Most of us are fluent in both temperatures, and driving - but most of us still couldn't figure out without converting whether we should build our decks with 4" boards or whatever the metric conversion for that is. Or - a perfect example from Percy above - I wouldn't have a clue as to where to raise my hand to 142 cm.

I learned temperatures by feel because it was really easy & we never hear the temperature on our news in anything but celcius. It became very easy to adapt to know now you need the bathing suit for 40 degrees, shorts & t-shirt for 30 degrees, a jacket for 15 degrees, and a winter coat for 0. And - oh yes, we still stay inside when it's 40 below when we visit mom in the prairies in the winter.

Driving was easy too, because we just HAD to get used to it, and besides most cars we buy here still have both km and mph on them, so you can always drive that way if you have to. And because we got the feel for driving, we also came to know it was too far to walk 10 km to go to your friend's house, best to get in the car.

But cooking in grams & kg and still boggles us - at least us older folk. For one thing, most of my cookbooks are either from the US or I've had them a long time, as they are in imperial, not metric. My measuring spoons say both, so it's easier to keep to the old system. And no matter what the package says a litre of milk will always be a quart of milk and if I get more - or less than I am expecting, I can't tell the difference.

And when one goes to a quilt shop, one still asks for 3 yards of that material. The sales girl rolls her eyes & says, sorry ma'am, I need it in meters, not yards. So I say, well OK then give me 3 meters and she does a little happy dance because she has now sold me more material than I need because I can't convert the darn measurement!

And same with weights. Someone tells me they weigh 67 kg, I say OK, should you diet or eat more french fries ? I have no feel for it.

Funny thing is, our kids - even though they learned both - seem to use the same ones as us. My son, just into his thirties, certainly learned the metric system, but still talks in inches & feet and lbs and ounces. But talks temperatures in celcius and distance in km. Guess we parents are more influential than we think! Either that or the teachers never really pushed the metric system either.

Great info and done with a sense of fun. Stumbled in here and read the back and forth with a smile! I almost bought a kilo of sandwich ham in Mexico a few weeks ago. I never buy 2.2 lbs. of sandwich meat. I stopped the sales girl. She was in a hurry to give me a kilo. I ended up with 1/2 a pound before I could stop her. I turned to my friend and we had a laugh. The sales girl thought we would assume we were getting a pound. Just goes to show that when traveling, one must have some understanding of the metric system or pay the price. :)

Thank you LyndaS not because you agree with me but because of the lovely story you told.

I can identify with everything you said,and you said it well.

I remember that none of us wanted the Metric System but our beloved Prime Minister of the day , knew what was best for us all.!!

I have been converting ever since the Metric system arrive .)

I was in Germany last year and when I reading the mileage ( oops Kilometers) on a highway sign ,saying 37 Kilometers to Dresden........... my mind quickly went
hmmm! 37 Kilometers, make that 40 Km.(because 40 is an easy number), now times 0.6( for the conversion) equals 24 miles , so just a few miles under 24 miles to Dresden.!!!!

I am sure many of us do it instinctively ,it's become second nature !!

Thanks again for the lovely story (PS ,I did not want to mention the French part, but I am glad you did .:)

I have a HEADACHE!!

SD

...well, as long as your temp's 37C :)

Or you can take two 325 mgm Asprins ! :)

Actually, in Canada we used to use the "close enough" method, which is double the Celsius temperature and add 30.

So 23 degrees Celsius x 2 = 46 + 30 = 76.

The actual conversion is 73.4, but you know, close enough.

We haven't seen this old thread for a while.

Yes nelle09 this thread is 7 years old but it is more difficult to divide or multipy by the 1.8 in your example.

I like the method at the top of the page by sdb2.

Only 3 countries in the world do us use metric, the USA being the major one.

I, for one am all about simple. Some of us don't have a head for numbers and so appreciate being able to use a truly simple formula to get an idea of what kind of temperature you'll be faced with when you walk out your door. When you're stuck in a foreign country with absolutely no frame of reference and nothing whatsoever familiar, something as simple as having an idea of what it's like temperature wise outside is important. I don't expect preciseness (and yes I know that's not a word as such) but it's nice to be able to wrap your head about something, anything, no matter how simple. I happen to be glad the US didn't go metric. Had it done so, there's a decent chance I would've never gotten out of high school LOL Not because Im stupid or anything. Far from it. But because I was born with a learning disability in math so no matter how hard I try or study or whatever, higher math will always be lost to me. So yes, I truly appreciate this little trick, cheating or not, imprecise or not. Thank you :)

I am very pleased to join this nice conversation. Measurement systems come from the general need to record and transfer information, the size of the area where it's used depends from the reach of the economy that stays behind... So, it's all relative!
Living in a Global Village, it makes no sense to have separate measurement systems, what do you think about? This said, nobody can say to have the best, as it's mainly matter of habits, as many of you highlighted... Unfortunately you need to adapt to local use moving country to country, not only for measurements, e.g. I am Italian and I have to adapt to English joining this conversation... I respect all ways, but counting in decimal or binary is it the same? End value is equal, but from practical point of view you need a lot of figures in binary. Coming back to imperial, it's a nightmare for conversion. Engineering is much better with metric. Mars Climate Orbiter was destried by unit conversion problem, its cost was 328M$. Metric is a rational system invented at Napoleon time. It's funny that Americans fought against British but were not able to free themselves from imperial habit. In replaying to question how tall I am in feet, I could but answer that in Europe feet are just for walking....

Well, I am seeing this old thread for the first time. It was very interesting and I got it by googling for a formula to convert temperature easier. So I appreciate the simple formulas.
As a 60 yr old living in Canada since moving from US at age 7, I can assure you that what Linda S wrote on Nov 13 2009, is right, completely.
That being said, Canada changing over was the best thing to do, but they didn't understand it would take generations. So I agree the USA (the greatest nation in the world) is backwards not to change to Metric. The earlier the better, because it will take a long time to get the "feel" for the measurements.
And we Americans do tend to have a certain pride in our ignorance.

Just opinions from my experience

Thank you so much for this easiest mathematical way to convert Celsius to Fahrenheit. I also went to school in the 70's and was told we/America was going to convert to the metric system in the near future. And as we all can see that had never happened. I took several math classes in Jr high and high school including algebra 1 & 2. Now 35+ yrs later all I know of the metric system is that a 5K walk is a 3.1 mile walk and I only know that because before I walked my 1st 5K walk, i simply asked somebody how far that was in American miles so I could be sure that I could actually walk that far. Your simple conversion helps me a great deal in the instance that I watch a lot of nature documentaries and at least 95% of them tell the story about the different terrains and seasons that the animals live in in Celsius. Now that I've read your trick to figuring that out quickly, I can know how cold it gets where the polar bears and penguin, etc live. And same with the animals and such that live in the very hot parts of the world. So again thank you so much for posting your knowledge onto those of us that can use it even if just for fun and not because I have to because I don't travel outside of America.
Regards,
Rhonda

Dear all, I entered in this conversation looking for a fast and simple way to convert F to C because my KIA car suddenly changed to the unusual F for Europeans. I do appreciate all the tricks, but I decided to keep F because I want to become familiar with it. Now I know that 45F is winter temperature without making any calculations, it became part of my way of thinking. It tought to me that I must be flexible and adaptable....

Thanks for this! I often look up and go to a C-F conversion webpage, not easy if there's no free WiFi, or while traveling.
Really appreciate it!

Thanks for this helpful trick of converting farenheit to celsius. I was born in America and moved to England when I was 9 and have lived here for 5 years yet am still getting to grips with the metric system.
My teacher once asked me how tall I thought I was and I knew at that time I was 4 and a bit feet so I told him I was 2 metres!!

Olivia

Livey_standish, you said you were born in America and moved to England at age 9, and you have lived there for 5 years. Are you saying you are only 14 years old? If so, you might be the youngest Fodorite ever.

althom1122 sums up why the USA has not made the conversion to the metric system: "I wish we'd gone metric back when it was being talked about. I was in junior high at the time and probably could have made the shift, although even then it would have been tough. Now (as an old dog) it would be much harder."

"Old dogs" inhabit Congress and make the laws. Old dogs don't want to learn new things. Public school students still learn metric system in almost every math and science class, but, unfortunately, it's largely a waste of time.


In 1866, the U.S. Congress authorized the use of the metric system and almost a decade later America became one of 17 original signatory nations to the Treaty of the Meter. A more modern system was approved in 1960 and is commonly known as SI or the International System of Units.
http://www.cnn.com/interactive/2015/...merican-story/

In 1968, Congress authorized a three-year study of systems of measurement in the U.S., with particular emphasis on the feasibility of adopting.
https://www.nist.gov/sites/default/f...tric/1136a.pdf

Congress passed the Metric Conversion Act of 1975 "to coordinate and plan the increasing use of the metric system in the United States".

The American National Metric Council (ANMC) was established in 1973 by the American National Standards Institute (ANSI) as a non-profit, tax-exempt organization for planning and coordinating metric activity in all sectors of the U.S. economy. The ANMC became a separately incorporated organization in 1976.
https://en.wikipedia.org/wiki/Metric..._United_States

The pyramid inch is a division of the measurement between north and south poles measured through the center of the earth. The meter is a division of the measurement between the north and south poles, measured over the surface of earth, I think the line runs through France, but, if you were to measure at another location, the distance between poles would be different due to the geology or topography, so the inch is a true unit of measure on earth.... Temperature, well, the metric would be a better choice if I didn't already know Fahrenheit as my go to scale.

Fellow baby boomers. what a mess! I live in the midwest United States. Illinois to be specific. I'm a retired RN. Irrelevant! It's what you grow up with that becomes your go-to. Not effective. So even though I'm no dummy, I sometimes need help. So...thank goodness there's an app for that!!

The easiest way to convert, and I'm surprised that it's not on here, my dad and I figured out. Take the C temp and double it, subtract 10% and then add 32. Everyone can do 10% of something. It's mathematically the same as doing the Cx9/5+32=F equation, only doesn't involve fractions. You're welcome. :)

When Britain went metric in the 1970s, a national competition to find handy tips for conversion produced two great winners: 'A liter of water's a pint and three quarters', and, more relevant to this discussion, a verse that tells you all you need to know if you only care about what to wear to suit the weather: '10, 15 and 21 - winter, spring and summer sun.' (Of course, this only works for Britain, not Arizona, Lapland, or Singapore.)

For Dlph311:
Please go back a bit and reread.
(You're also welcome!)

"Celia on Nov 12, 09 at 12:57pm
In my travels I have developed a "feel" for kilometers, so I don't need to convert them. But for temperature, I haven't been able to develop a feel, so I do what's described here, with a slight difference. I double the Celsius number, subtract 10% (that's where I differ from others) and add 32. That's close enough to let me know whether I want a swim suit or .."a.snow parka.

This thread is so old I don't know why I'm bothering, but Percy's post on Nov 12 is just ludicrous.

I'm a born and raised Canadian and there is zero truth to the notion that people here do not like the metric system. I cannot recall a single complaint since I was a small child and the system was quite new. Not ONE.

Also stupid: the idea of metric police. The country moved to a new system, and yes, stores were required to comply and a few did not. You can't have stores all using whatever system they like. There was no gestapo as Percy suggests but stores were required to use metric (they were allowed to have imperial as well, as long as the metric weight was listed. Horrors!).

Also, if you know someone who raised in Canada and learned metric in school, I cannot imagine how that person would end up only understanding miles given that no one in this country uses miles for distance or speed. Ever. Maybe his parents were resistant and only used miles at home? Or this is just BS? My parents would be in their eighties now if alive so they grew up with imperial and learned metric in their forties, and after a few years to adjust, they only used C for temperatures, and kilometers for distance and speed. So this nephew that only uses miles in Canada is an isolated case and not the norm. I haven't heard a Canadian use miles for anything in the last couple of decades at least.

We do have a quirk. Canadians tend to use feet and inches for human height and pounds for human weight (that is changing). And the British still use stone for human weight. A quirk does not mean we are not using metric, it's just a quirk.

Also, if none of your Canadian friends talk to you in metric, it's because they know you will not understand it. Canadians are hyper aware that American's don't understand it so we usually will look things up in imperial when talking to you. I have an American aunt and I always look up the temperature in fahrenheit when I'm relating it to her. It's polite. Canadians are kind of known for being polite. Also, we call is celsius. No one calls is centigrade. Not that it matters. I get what you meant.

I have noticed that sometimes when Americans confront a change that Canada has already gone through, they speak authoritatively about how it really went wrong for Canada and they have all this inside information on how Canadians feel. When Obamacare was coming in, all I heard was how Canadians hate our health care system, and we can't even choose our own doctors (total hogwash, and there were so many other lies told to Americans about our health system around that time). Please, leave us out of it and speak for yourself, please. It's so frustrating to always read how Canadians feel and it has no relation to what is going on here. And dont' assume that a couple of people you know represent a country.

A final note. "Oh yes, Canada thought their trade would boom internationally when they converted to metric.... A government study later on proved that was not the case. "

WTF? I just asked around. No one has ever heard of anything to support that statement. I'd love to see some evidence on that one. Our economy is just fine, thanks. A couple of years ago our dollar was worth quite a bit more than yours. Not right now. Still, better than many countries. I'd love to see that study. I'm a university researcher and could find nothing to support this. Link please! Can't wait to read it.

The shortcut is actually calculating a value for Fahrenheit that's equal to (1.9C + 32), rather than the actual (1.8C + 32).

The formula IS Fahrenheit degrees minus 32 times 5/9!
212-32=180 180 times 180=180 divided by9=20 times 5=100!

The other formula is Centigrade degrees times 9/5 + 32.
100 times 9=900 divided by 5=180+32=212 viola!

To sdb2 on Nov 11, 09 at 9:53am

The Fahrenheit degrees = Centigrade times9/5 or 100 times 9=900 divide by 5=180+32=212. Viola

Several people have posted that doubling the Celcius value, subtracting 10%, and then adding 32F gives you 1.9C + 32.

That is not true.

The procedure gives you 1.8C + 32 and is a valid way of converting from C to F.

Subtracting 10% is the same as multiplying by 0.9. So, if you double and then multiply by 0.9 you get 2 * 0.9 = 1.8, not 1.9.

Another way of looking at it is that 10% of 2 is 0.2. Subtracting 0.2 from 2 gives you 1.8.

Let's do an example to prove it works.

100C -> double it gives 200, subtract 10% (or multiply by 0.9) gives 180, then adding gives 212F which is the correct answer.

QED