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Q: Celsius vs. fahrenheit -- Why? ( Answered 5 out of 5 stars,   6 Comments )
Subject: Celsius vs. fahrenheit -- Why?
Category: Science > Instruments and Methods
Asked by: shaneh-ga
List Price: $4.00
Posted: 02 Jul 2002 23:19 PDT
Expires: 01 Aug 2002 23:19 PDT
Question ID: 36122

All I want to know is why the fahrenheit system was adopted rather
then the much simpler celsius system.  The answer to this is probably
related to the answer of "Why do we use imperial mesurements, opposed
to much simpler metric." I just want to know why... I'm guessing it
had something to do with rebellion of the US from england.. but I have
no evidence.
Subject: Re: Celsius vs. fahrenheit -- Why?
Answered By: leli-ga on 03 Jul 2002 02:13 PDT
Rated:5 out of 5 stars
Hi Shaneh

Thanks for the interesting question.  You are quite right that this is
part of the whole imperial versus metric thing.

It may surprise you to learn that the US signed the "Treaty of the
Meter" in 1875 along with all the major industrialized nations.  This
was a commitment to move towards metrication including Celsius for
everyday temperature measurement.  There's a summary of its major
points at:

But things didn't quite work out that way.

A little bit of history first:

Fahrenheit devised his temperature scale and invented the mercury
thermometer nearly thirty years before Celsius thought of his system
1714 as opposed to 1742.  To begin with it was mostly just scientists
who were interested in accurate temperature scales.

The French were the first to make a formal proposal that the Celsius
system (also known as centigrade) should be the official national
standard.  Although they started the process before 1800 things didn't
really settle down until their political situation stabilised around
the middle of the nineteenth century.  From then on Celsius spread
through many non-English speaking countries.  By 1880 most of Europe
and South America was metric.

But the English-speaking countries did not exactly move fast after
signing that 1875 meter treaty I mentioned above.

Great Britain, South Africa, New Zealand, Canada, Australia and
Ireland all waited till the sixties and seventies to implement
metrication policies and make Celsius official.  One Irish source says
that the US inherited the Imperial system from Britain. They also
describe the US and UK as sharing an emotional attachment to the old
units.  See:

In the UK Celsius and metrication caused uproar and consumer
resistance.  Although weather forecasts are generally given in
Celsius, some daily newspapers still include Fahrenheit in weather
reports as many people are more comfortable with that.

There is a desire in some quarters for the US to adopt Celsius, kilos
etc.  See:

I guess the arguments against making the change are the same as those
so beloved of some Brits.  They include the expense of changing
measuring equipment, expense of retraining staff, buying new
textbooks, persuading the public to accept change, disappearance of
tradition and so on.

Hope this answers your question – let me know if you need any


Sites with further information:

Search terms used: 
Combinations of: celsius fahrenheit temperature standards policy
"treaty of the meter"

Request for Answer Clarification by shaneh-ga on 03 Jul 2002 02:24 PDT
Hi leli, 

Your answer was great! If you could please expand more on this part:

"One Irish source says that the US inherited the Imperial system from

Thats what I was most interested in... Why, in the beginning, did we
choose to use the fahrenheit system?  If both units of measure existed
prior to the creation of the US, why did we adopt fahrenheit in the
first place? All you really need to do is provide me with the "Irish

Also, the link to did not work.. 


Clarification of Answer by leli-ga on 03 Jul 2002 04:46 PDT
The "Irish source" is on the site that didn't work for you - at: .
But I will see if I can find anything more specific on exactly how
Fahrenheit got established in the English-speaking countries.

Clarification of Answer by leli-ga on 03 Jul 2002 07:19 PDT
Hi again Shane

I really respect your desire to get to the heart of the matter but I'm
afraid there may be no easy answers out there.  There is definitely a
link between speaking English and using the Fahrenheit scale.  As a
German website  says - Fahrenheit's scale applies in the anglo-saxon
countries.  See:
I have discussed this with a professor who knows a lot about the
history of science and his comment was that there is sometimes an
element of randomness in such matters.
I'm afraid I can only refer you to possible sources of further

Websites with lists of archives and other resources on the history of

Or possibly a book with some of Fahrenheit’s letters?

Let's hope someone somewhere will be able to contribute a comment that
clears this up. Or is the truth lost in the mists of time?
shaneh-ga rated this answer:5 out of 5 stars

Subject: Re: Celsius vs. fahrenheit -- Why?
From: robertskelton-ga on 03 Jul 2002 04:04 PDT
The link works for me. Perhaps try it again.
Subject: Re: Celsius vs. fahrenheit -- Why?
From: mwalcoff-ga on 03 Jul 2002 05:45 PDT
Just a comment -- I don't know that Celsius is "simpler" than
Fahrenheit. The Celsius scale, of course, is based on the freezing and
boiling points of water. That is great for hydrologists, but not
particularly helpful for everyday uses. A temperate-zone city might
range in temperatures from -15 to 35 -- nothing particularly helpful
there. On the other hand, Fahrenheit works perfectly for weather. That
city will range in temperature from about zero to about 100 Fahrenheit
in a year. If it's below zero, or above 100, you know it's really cold
or really hot. Plus, Fahrenheit allows you to divide a map of the U.S.
neatly into temperatures by 10-degree intervals.
Subject: Re: Celsius vs. fahrenheit -- Why?
From: hedgie-ga on 03 Jul 2002 07:37 PDT
The person responsible may well be Jefferson. 

Here is a quote 

... Jefferson's report of 1790, on weights, measures
    and coinage, contains a highly suggestive passage on the subject
of rectilinear lines. In discussing measures  of capacity (quarts,
gallons, etc.) ..

Both system (metric and imperial) existed when US was formed. US
the metric conventionand was first country to have metric currency
(100 cents = $1)
but Jefferson (who was given the task to recommend  system of
was afraid that it would give France to much influence to adopt meter
(meter was defined based on meridianpassing through Paris) and did not
recommend adoption of metric system.
 That was a mistake for sure. But, even if he would, the cultural
inertia would  prevail:
System of measurement is part of the language, and  adoption of 
implied adoption of britsh units.

By the way, Farnheit's scale was not the first at all.   

Here is the short history

which avoids often reported legends. Olaf Romer, astronomer
 (same guys  BTW was first to estimate speed of light) 
placed the zero of his scale to one particularly  cold day of
particularly cold winter in Denmark,
which explains why Farenheit scale, derived form Romer's is well
adopted to weather measurment.

In Romer's  time 'round numbers'  like 60 and 360 still had strong 
effect in astronomers , which is why, to this day,  we measure  T
in 'degrees' even  though the scale is linear. 

 The  Celsius scale, like other metric units, is based on the
objective properties and in Kelvins we finally dropped the 'degree'.
Subject: Re: Celsius vs. fahrenheit -- Why?
From: shaneh-ga on 03 Jul 2002 12:16 PDT
Hedgie: ***** Five stars for you.  I appreciate you taking the time to
share that!!! Very, Very, informative!!!
Subject: Re: Celsius vs. fahrenheit -- Why?
From: leli-ga on 04 Jul 2002 01:47 PDT
Yes, thanks to Hedgie for bringing Jefferson into the discussion. 
Jefferson was enthusiastic about French science but disapproved of
both their pre-revolution government and "Bonaparte's dumb
legislature".  His interest in both science and minute detail
contributed to his 1790 report on measurement to the House of
Representatives while Secretary of State.
You'll find it at:

Here you'll see he was proposing a kind of decimalisation but not the
French kind.  He wanted a 10000 foot mile and a 10 ounce pound.
But it doesn't mention temperature measurement.  

One small extra point is that in the 1790s he was recording the
temperature in his Monticello farm diary in Fahrenheit.  See:
Mr Jefferson, by Albert Jay Nock. Hallberg (1983) ISBN 0-87319-024-6

And, Shane, thanks for the five stars.  If you find any more pieces of
the puzzle, I'd be delighted to know about it.
Subject: Re: Celsius vs. fahrenheit -- Why?
From: blanketpower-ga on 29 Aug 2002 23:07 PDT
This is what I was told by my high school science teacher twenty-six
years ago... can't vouch for whether it is 100% accurate or not, but
the old buzzard would be surprised to know that I actually did listen
to him.

The Farenheight scale was based upon two temperatures - human body
temperature (100) and the temperature at which salt-saturated water
freezes (0). The numbers were not absolutely accurate - for example,
"normal" human body temperature is now known as 98.6 Farenheight
(rather than 100) now that measuring devices are better, but the two
reference points just mentioned were the idea behind the original

A more "scientific" scale was developed using pure water as the
standard. The freezing point of pure (distilled) water was set as the
zero-point. This is considerably warmer than the freezing point of
salt-saturated water used for the older scale. The boiling point of
pure water at one atmosphere of pressure was set as the "100" mark.

The Farenheight scale is the older one. Both Britain and the colonies
(including the USA) used this means of measurement. Britain converted
to metric a couple of hundred years later in the late 1970's (largely
related to the need for a common European standard of weights and
measures) but the USA has so far resisted the change-over.

A convenient way of converting the scales if you are good at mental
math... to go from Celcius to Farenheight, double the Celcius,
subtract ten percent, then add 32.  Example> 20 Celcius ---> 40 --->
-10% = 36 ---> +32 = 68 Farenheight.

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