Talk:Calorie/Archive 2

Archive 1

Archive 2

Calories and the Metric System. Countries and use....

It's interesting that although the Calorie is based on the Metric system and designed to fit in with it, it now seems to be officially rejected by the Metric authorities...

Since it's based on the gram and the Celsius degree, it's a perfect match for the Metric system - just as a mililitre is the same as a cubic centimeter and for water weighs one gram. And a litre of water weighs one kilogram. Whereas the joule has no such direct connection.

Not really; the crucial detail you're missing is that SI is based on the direct combination of its base units. That the ml is the cm³ is indeed a consequence of relevant definitions; the litre is defined as one thousandth of a cubic metre (equivalently, as a decimetre cubed; but almost no-one ever mentions the decimetre except in this formula and many are familiar with decilitres, as they're a practical unit in many contexts, and decimetre sounds too similar to it, with the lamentable result that I've heard (probably more often than the correct form) the litre's definition given as "a decilitre cubed", from which one may infer that litre is a pure number, the square root of 1000 – but I digress) so the millilitre is indeed the cube of the centimetre. In contrast, a litre of water merely happens to weigh approximately one kilogram; it's undoubtedly not a coincidence (someone surely chose one of the units to make this approximately right) but it's not the definition (contrast the UK gallon (or Queen Anne beer gallon; the US uses a Queen Anne wine gallon of 231 cubic inches) which was defined as the volume of 10 lb of water under specific conditions). Given the units of mass, length and time, one arrives at a natural unit of energy, Joule = kg.m.m/s/s. One could have then chosen, as unit of temperature, the change in temperature that one Joule produces in one gramme of water; however, instead, they chose one hundredth of the temperature difference between the boiling and freezing points of water; since these choices give different answers (the latter is about 4.2 times the former), the specific heat capacity of water is about 4.2 J/g/K rather than about 1. SI doesn't officially care about making water's properties have tidy values – and, in general, you can't do it for all of them, anyway – so it's not enough that the calorie is based on gram and Kelvin: it's also based on the specific heat capacity of water, which isn't a defined unit of SI. So SI prefers the unit of energy that's based on the kg, metre and second. Eddy 84.215.6.188 (talk) 15:09, 11 July 2011 (UTC)

It would be interesting to see a list of which countries use KJs vs. Cals in food labeling. I know that in the States and Canada Cals are used exclusively and that in Europe the Calorie is still the unit used, though KJs are sometimes given as well. But in Australia and New Zealand, the KJ has apparently become the primary unit for measuring food energy, though Cals are often listed as well.

Does anyone have information for other countries?... —Preceding unsigned comment added by 67.54.230.17 (talk) 03:55, 15 June 2008 (UTC)

That would be an interesting list. No, the joule has no such connexion. It's got a much more direct one:

1 J = 1 kg·m²·s⁻²

thus fits in a whole lot better than a unit whose definition depends on how warm you want your gram ... or kilogram ... of water. JIMp _talk·cont 09:13, 21 June 2008 (UTC)

Though SI units are prevalent in Denmark, energy in food is always listed as both kcal and kJ. Teglsbo (talk) 12:17, 17 August 2008 (UTC)

... as required by legislation (see references in food energy article) in all EU countries. Markus Kuhn (talk) 12:57, 17 August 2008 (UTC)

SI is also used in Australia. JIMp _talk·cont 11:29, 27 January 2009 (UTC)

Deprecation

The following was removed by an anon.

Since the many different definitions are a source of confusion and error, all calories are now deprecated in favour of the SI unit for energy, the joule.

But aren't they depreciated? If so, by whom? Can we not source & clarify this? JIMp _talk·cont 16:32, 27 February 2009 (UTC)

s/depreciated/deprecated/ ! (section title fixed) A thing depreciates as its value goes down; one deprecates a thing when one has decided to discourage folk from using it. Eddy 84.215.6.188 (talk) 15:33, 11 July 2011 (UTC)

Color

What is the purpose of the funny coloring of the conversion factors in "Variations"? --A. di M. (talk) 15:14, 2 March 2009 (UTC)

Less confusing now (i.e., big C vs small c). —Preceding unsigned comment added by Port Tiger (talk • contribs) 20:52, 17 July 2009 (UTC)

Calorie vs calorie

"The kilogram calorie, large calorie, food calorie, Calorie (capital C) or just calorie (lowercase c) is the amount of energy required to raise the temperature of one kilogram of water by one degree Celsius."

This is wrong, Calorie with a capital C is different from calorie with a lowercase c. —Preceding unsigned comment added by 72.130.55.225 (talk) 18:34, 20 July 2009 (UTC)

This is a distinction that is not followed by everyone (no surprise since it amounts to inventing your own capitalisation rules and doesn't work if the word would be capitalised anyway, e.g. at the beginning of a sentence) and thus the article is correct. It would have been better if they'd called the big calorie a kcalorie (except for its ugly orthography) ... it would best if they'd drop it unit entirely in favour of the kilojoule. JIMp _talk·cont 00:32, 4 September 2009 (UTC)

Note also that the big calorie is "older" than the small calorie; scientists created the kilogram calorie before the gram calorie. So rather than suggesting it would have been better if they had called it a "kcalorie" or something, I'd say it would have been better if the chemists and physicists who later started to use the small unit had called it a "millicalorie".

In any case, the small calorie is rarely used any more, so there is no good reason whatsoever to use strange (and often ineffective, as Jimp has pointed out) capitalization rules to make a distinction that doesn't matter. Almost nobody does that in any case--that strange capitalization is barely common enough in actual use to even warrant mention at all in the article. It is the only large calories which remain in common use. Gene Nygaard (talk) 02:02, 31 December 2009 (UTC)

Yes, that would have been much better. Redefining stuff is a recipe for confusion. The same thing happened to the billion. JIMp _talk·cont 20:50, 15 July 2010 (UTC)

How much is 2 calories?

if one calorie heat up one liter one degree Celsius; then how many liters and degrees does two calories make? is it that two calories makes 1 liter 2 degrees hotter, or will it make 2 liters one degree hotter, or is it both? 21:56, 15 March 2010 US Eastern —Preceding unsigned comment added by Populer208 (talk • contribs)

Both. JIMp _talk·cont 09:10, 15 April 2010 (UTC)

Nicolas Flamel

Invented the calorie? Really? 98.185.253.158 (talk) 06:12, 24 March 2010 (UTC)

Which is the real calorie?

Peasaep has rewritten the intro. The current version seems to suggest that it is the gram calorie which is the "real" calorie (so to speak) and the kilogram calorie is just another unit sometimes referred to as a calorie. How true-to-life is this picture? In countries which still cling to this tired old unit aren't things often labelled using the 4.2 kJ calorie? Do we have to pick a favourite? If both are (or have been) used, why can't treat them equally? We're writing about the real world not an ideal one ... (in an ideal world there'd be no such unit anyway). JIMp _talk·cont 20:20, 30 June 2010 (UTC)

I believe "calorie" refers to a gram calorie, with "Calorie" or "kcal" referring to the kilogram calorie. See e.g. A Dictionary of Units of Measurement. I think it's a good idea to use this definition as standard and then elaborate on some of the ambiguities and incorrect usages in the body of the article, rather than compensating with vagueness is the intro. For example, the current (modified since my edit) intro states that:

The calorie is a pre-SI metric unit of energy based on the specific heat capacity of water. Definitions vary according to the mass of water used and the precise thermodynamic conditions considered.

This tries to hard to avoid using any one specific definition that it barely says anything important about a calorie. Imagine if the joule page defined a joule as "a unit of energy based on newtons, objects and meters" instead of the beautifully concise "the energy exerted by the force of one newton acting to move an object through a distance of one metre". Peasaep (talk) 12:39, 14 July 2010 (UTC)

OTOH, the Joule is well-defined, which is why it's possible to write such a concise definition; while the calorie's definition is (even ignoring the whole short/long complication) fuzzy, which makes it harder to be concise without being Wrong. (Einstein: everything should be made as simple as possible and no simpler.) Still, I grant it would probably be better to say "The calorie is the amount of energy that raises the temperature of a unit mass of water by one Kelvin." before diving into the unfortunate complications due to two choices of unit of mass and diverse choices of the temperature interval over which to measure the unit. Eddy 84.215.6.188 (talk) 15:45, 11 July 2011 (UTC)

Also, just to address some of the previous comments, I disagree that calorie always refers to kcals in the "real world". If you check pretty much any result on the first page of google results, as well as google themselves, they clearly state that one calorie is a gram calorie, equal to approx 4.2 joules (not kilojoules!). People seem to be suggesting that because some food producers incorrectly use the term calorie, we should ignore the facts and redefine what a calorie is, which is not right at all. Not only that, but most of the nutritional information I checked (e.g. the example on Food energy, the info put out by McDonalds) is printed so that it clearly indicates Calories or kcals are being used. Misuse of the term calorie certainly deserves a mention, but it shouldn't be used as an excuse to water down the opening paragraph into vague waffle. Peasaep (talk) 16:55, 15 July 2010 (UTC)

No, we are not and should not be in the business of redefining anything. The job of an encyclopædia is to reflect what is out there. If there are various different definitions floating around, this is the reality, we can't just pick the best one and label anything that deviates from this "wrong". The comparison to the joule is not really fair since the joule has a clear-cut definition. The calorie, on the other hand (or so it appears), lacks a single definition. It doesn't make for a vague waffling intro to point this fact out: this in itself is an important fact about the unit, one of the major disadvantages with using it.

Gene Nygaard (who seems pretty knowledgeable about units of measure) above states that "the small calorie is rarely used any more". He also suggests the Calorie/calorie distinction is not widely followed (and this would make sense since, grammatically speaking, it's pure nonsense: it's no proper noun). Who's right? We need something a little more substantial than Google searches and our own experiences with food containers. JIMp _talk·cont 20:50, 15 July 2010 (UTC)

Reliable sources that state "one calorie is ~4.2 joules":

• p39 of Dunford, M. and Doyle, J.A. (2007) Nutrition for Sport and Exercise
• p178 of Rastogi, S.C. (2003) Biochemistry
• p30 of Bodner, G.M. and Parude, H.L. (1989) Chemistry, an Experimental Science
• Further reasonably reliable web sources 1 | 2 | 3 | 4

Most of these sources also clearly describe the difference between a calorie and a Calorie (capital). Sources that disagree: "Gene Nygard who is pretty knowledgeable about units" and a few dieting forums. Are you really suggesting that Gene Nygard's opinion is more substantial than all of the sources that can be provided by a simple Googling?

One of the problems with trying to allow a calorie to be defined as 4.2 kilojoules is that it then suggests that it may be valid to define a kilocalorie as 4,200 kilojoules, increasing the confusion even more. It certainly deserves a mention that one of the only remaining uses for calories these days is to measure the energy content of foods, and that in this context people always mean kilocalories (even when they simply say calories), but I don't think there's any need to over-obfuscate the actual definition of a calorie. Take a look back a few years ago here, when I think the article was much clearer. It defines small and large calories, and mentions that in food energy, people are always referring to large calories. Was there anything about the old version that you found particularly objectionable? Peasaep (talk) 06:29, 16 July 2010 (UTC)

Wow, it seems to get even better the further back you go. Peasaep (talk) 07:35, 16 July 2010 (UTC)

Nutrition and food labelling is mostly where this unit still remains in use, right? In this context a ~4.2 kJ unit is implied, right? So whenever people say "calorie" they really mean "kilocalorie" and are just forgetting the "kilo-" ... no, if they say "calorie" and mean ~4.2 kJ, they're not wrong, they're simply using a different definition. I'm not suggesting we obfuscate the actual definition of a calorie: there is no actual definition ... no definitive one.

No, Gene doesn't trump reliable sources. I'm sure he'd be able to dig some up though, he must have based his opinion on something. Here's what I've found.

• http://www.trueknowledge.com/q/how_many_calories_in_joules
• http://health.howstuffworks.com/wellness/diet-fitness/weight-loss/calorie1.htm
• http://quezi.com/6403

Not that substantial, no, but it does support the propositions that the term can refer to the larger unit and that the capitalisation rule is not widely followed.

"One of the problems with trying to allow a calorie to be defined as 4.2 kilojoules ..." ... one of the problems is that we're not here to allow or disallow anything. I'm sure the article could be made clearer but it should be a clear reflexion of the real world. In the real world, like it or not, the unit is ill-defined. This is an important fact, a major cause of confusion and disadvantage with the use of the unit.

One objection to the first old version you mention was the stuff about its being a unit of heat but this is a different issue and one I've already discussed above. The older "better" version contained stuff that didn't belong here but I suppose you were looking at intro as opposed to the trivia and labelling sections. JIMp _talk·cont 08:47, 16 July 2010 (UTC)

I actually have no problem with the latter two references. I've edited again to try and take a similar approach by providing the clearest and most unambiguous information first by describing gram and kilogram calories and only then explaining the contexts under which "calorie" can refer to each. Let me know if there are still issues. Peasaep (talk) 15:48, 16 July 2010 (UTC)

I think we're moving in the right direction but, yes, there are a few things I'd like to bring up. Let me start the list with some of the more trivial.

• We've got a bit of an overlinking problem: Joule is linked to three times (four if you count the kilojoule link), International System of Units is linked to twice, Water is linked to twice, ... resolved
• Perhaps metric prefix would be better (since the calorie is non-SI) ... this is probably the better term in general but that's a different battle. resolved
• It's noted that the small calorie is exactly 0.001 large calories but the large calorie hadn't been introduced by this point. We then go on to note that the large calorie is exactly 1000 small calories ones: basically saying the same thing twice. resolved
• We're giving an "approximate" conversion to an unrelated (albeit the SI) unit before the exact conversion to a related one ("This is about 4.184 kJ, and exactly 1000 small calories.") which seems a little backward.
• Of course there isn't much approximate about 4.184 joules ... nope, that's pretty much the termochemical calorie exactly. The phrase "about 4.184 J" to me implies a give or take of 0.01% or so.
• We're no longer mentioning the variation in definition due to using water at different temperatures in the intro. If the termochemical calorie is somehow special, tell us why and mention that there are others.
• Perhaps I'm being pedantic but "the kilogram calorie is known as the 'kilocalorie'" just doesn't ring true to me. The prefix "kilo-" can be tacked on to any metric unit (unless there's already a prefix, of course) and so you could have a kilogram kilocalorie (about 4.2 MJ) ... why not? Of course, it would be uselessly big and confusing, which would explain why this is avoided. My point is that the term kilocalorie is not another name for the kilogram calorie but (as logic surely dictates) means "1000 calories", which we can pretty-much always assume are small calories. The kilogram calorie is equivalent to but not synonymous with the (gram) kilocalorie. I may be being picky but if it's clarity we're aiming at, straightening this out might even help.
• How common really is this strange capitalisation rule and is there not a clearer expression we could use instead of "referred to as a Calorie (capital 'C'), or just a calorie"?
• I notice that a couple of things are missing: the pound calorie is gone & so is some of the history (e.g. the large calorie came first).

JIMp _talk·cont 08:09, 17 July 2010 (UTC)

You mention the large calorie coming first – do you have a citation for that ? It sounds like a relevant factor in the history: what was the original definition ? (Especially in light of the later divergence.) It's also worthy of note that kg (despite its name) is the base unit of mass, in particular the unit of mass used in defining the Joule, so would indeed make more sense (little though this has to do with reality or the history of the unit) as mass unit to multiply the heat capacity of water by in the course of obtaining an energy unit from it. Eddy 84.215.6.188 (talk) 15:59, 11 July 2011 (UTC)

I see Nicolas Clément says the same, but also lacks citation; it also says that 1929 is when a BAS committee proposed the short calorie as replacement unit – so now we know who to blame for all the subsequent confusion ! Eddy 84.215.6.188 (talk) 16:17, 11 July 2011 (UTC)

The confusion predates 1929. "The history of the calorie in nutrition" published in The Scientific monthly volume 15 in 1922 discusses the difference between small and large calories and their usage in literature in the 1800s. 96.231.167.205 (talk) 07:55, 22 August 2011 (UTC)

I don't know about the kilogram's being the base unit of mass. It is the base unit in the SI but the calorie is not an SI unit. JIMp _talk·cont 23:46, 22 August 2011 (UTC)

Suspected error for "International Steam Table calorie (1929)"

In the table of different standards, the International Steam Table calorie (1929) is given as "≈ 4.1868 J" but the notes say that it's

1/860 'international watt hours' = 180/43 'international joules' exactly.

Unless the 'international watt hour' and 'international joule' are something other than the Watt.hour and Joule respectively, this ratio gives 4.18604651 J, for which 4.1860 J is a faithful approximation while the given 4.1868 J is not. It would appear to have been copied from the following entry in the table. Is anyone in a position to check the original sources ? Eddy 84.215.6.188 (talk) 16:13, 11 July 2011 (UTC)

More precise definition

"The massive calorie or gram calorie (symbol: cal)[2] approximates the energy needed to increase the temperature of 1 gram of water by 1 °C. This is about 4.2 joules."

This amount of energy actually varies based on the temperature. The more precise definition includes information about the starting and ending temperatures and about pressure conditions.

N/M, the chart already elaborates on this. My mistake. I should just delete this ...— Preceding unsigned comment added by 72.130.93.49 (talk) 12:44, 25 May 2012 (UTC)

Nutritional contexts

On 28 August 2012 2001:5C0:1501:0:C4AC:D899:819A:7761 changes

The gram calorie is not used in nutritional contexts. Instead, the large calorie is used. In this context calorie and kilocalorie are equivalent.

to

In the United States, the gram calorie is not used in nutritional contexts; instead, the large calorie is used. In this context calorie and kilocalorie are equivalent. In European countries, the opposite is applies.

but is soon reverted by SudoGhost for lack of a source. This is a fair call, info should be sourced, but do we have a source for the original statement? What exactly do we want to say anyway? It seems to me that neither version correctly describes what goes on.

In nutritional contexts some use calories and some use kilocalories (others use kilojoules). Those who use calories are basing their definition on the kilogram. Those who use kilocalories base their definition on the gram. One small kilocalorie, equaling a thousand small calories, is equivalent to one large calorie (1 kcal = 1,000 cal = 1 Cal). Context indicates which definition is being used. Thus in nutritional contexts the terms calorie and kilocalorie are equivalent.

I think we want to say something like the above. What are we saying, though?

• "The gram calorie is not used in nutritional contexts."

Well, it's not used as such but it does form the basis for the (gram) kilocalorie, which is used.

• "Instead, the large calorie is used."

This is not true; some use the (gram) kilocalorie and others use the kilojoule.

The edit which was reverted, it seems to me, was an attempt at addressing this. It fell short of doing so, however, on a number of counts.

• It was framed as a US vs Europe thing but the world consists of more that the US and Europe.
• It seemed to imply that the gram calorie is used as is (i.e. without the "kilo-" prefix) in Europe.
• Instead of clarifying what was meant by "In this context calorie and kilocalorie are equivalent." it became even more obscure.

It would be nice to have some sources but until we can find them, allow me to replace the unsourced unclear and incorrect statement with an unsorced but clear a correct version. JIMp _talk·cont 04:35, 31 August 2012 (UTC)

Need More Background on The ThermoChemical Calorie.

The International Table Calorie is now defined as 4.1868 Joules in accordance with the determination of the fifth International Conference on Properties of Steam (London, July 1956). This detaches the calorie from the properties of water and yet retains a value very close to the properties of water.

The ThermoChemical calorie is defined exactly in terms of Joules as well but uses 4.184 Joules. Who gave this definition and what was the reason? What does "ThermoChemical" imply? 134.131.125.49 23:36, 18 July 2007 (UTC)

Bichowsky and Rossini introduced the concept of a defined calorie for use when converting experimental thermochemistry results obtained in joules into the traditional unit of calories, this has since become known as the thermochemical calorie of exactly 4.184 joules.

Francis Russell Bichowsky; Frederick D. Rossini (1936). The Thermochemistry of the Chemical Substances. New York: Reinhold. p. 9. Retrieved 21 January 2013. In order to satisfy the popular demand for the calorie as a unit in calculations and tabulations, and at the same time depart as little as possible from the fundamental unit of energy, the joule, in terms of which all accurate thermochemical measurements are actually made, we have used in this book a defined calorie, that is, one which has no actual relation whatever, except incidentally and historically, to the heat capacity of water. {{cite book}}: Cite has empty unknown parameter: |1= (help)

Nerlost (talk) 04:40, 8 February 2013 (UTC)

Could there be a typo in the FAO source?

The FAO source defines thermochemical calorie twice as 4.1840 J exactly. But when refering to the "nutritional calorie" as "basically" the thermochemical calorie, the source indicates the factor of 4.182 J per thermochemical calorie. I am thinking the 4.182 factor was a typo and that 4.184 is the correct factor. maybe. 151.121.65.250 11:24, 28 January 2011 (UTC)

Yes, I agree there is a typo in the FAO source. A definition for the IUNS calorie was added to the Calorie page on 9 March 2006. A source for this definition was added on 28 May 2008.

IUNS calorie = 4.182 J This is a ratio adopted by the Committee on Nomenclature of the International Union of Nutritional Sciences.
FAO (1971). "The adoption of joules as units of energy". While the nutritional calorie has not been defined, basically it is the thermochemical calorie. The standards used in calorimetric work in nutrition is ultimately the heat of combustion of an internationally graded standard benzoic acid. This is primarily expressed as joules per gramme mole and secondarily as thermochemical calories per mole derived by dividing by 4.182, a factor which has been approved by the Committee on Nomenclature of the IUNS.

This one sentence in the FAO source does contain the value 4.182, but I believe this is a typographical error in the original document and the value should be 4.184. The value of 4.184 is used in four other paragraphs in the source document as the exact conversion factor, for example it states

"The Committee on Nomenclature of the International Union of Nutritional Sciences concluded that most nutritionists use the thermochemical calorie which equals 4.1840 J exactly."

The FAO source is one working paper from the agenda for the FAO/WHO Ad Hoc Committee meeting. ( "FAO/WHO Ad Hoc Committee of Experts on Energy and Protein Requirements and Recommended Intakes, Rome, 22 March - 2 April 1971, Documentation for the Meeting". Retrieved 21 January 2013. ) The FAO/WHO Ad Hoc Committee's report, published in 1973, uses 4.184, it simply states: ( Energy and Protein Requirements : Report of a Joint FAO/WHO Ad Hoc Expert Committee, Rome, 22 March-2 April 1971 (PDF), Geneva: FAO and WHO, 1973, pp. 12–13, retrieved 21 January 2013 )

Many international and national organizations have recommended that all forms of energy should be expressed quantitatively in terms of joules, and the Committee decided to follow this recommendation but to express values in both joules and calories, the traditional unit of nutritionists. The usual unit of energy in nutrition studies is the kilocalorie (10³ calories), and hence 1 kilocalorie (1 kcal) = 4.184 kilojoules (kJ).

Once it is accepted that 4.182 is a typographical error and that the 4.184 joule thermochemical calorie was intended, and in the absence of a published source from the IUNS, then there is no new definition of an IUNS Calorie, and it should be removed from the Wikipedia page.

Nerlost (talk) 06:40, 31 January 2013 (UTC)

Kilocalorie given short shrift

There's almost no mention of the kilocalorie. It's excluded from the "large calorie" section, on the dubious grounds that it's a "different but equivalent unit", but it doesn't have its own section. This makes no sense, as kilocalorie is a very common unit in science. --Jtle515 (talk) 20:49, 12 November 2012 (UTC)

Isn't the third paragraph mention enough? Is it really that common a unit in science? I would dispute that the grounds that it is a different but equivalent unit to the large calorie are dubious. "Kilo" means 1000 so a kilocalorie is 1000 calories. If these 1000 calories equal ~4.2 kJ, then that's 1000 small calories. 1000 small calories equal one large calorie but the definitions are different. Thus I would argue that the 4.2-kilojoule kilocalorie doesn't belong in the large calorie section. If it needs more mention, put it in the small calorie section. JIMp _talk·cont 09:23, 14 November 2012 (UTC)

I just added 'kilocalorie' and removed the comment "<!--Not "kilocalorie", this is the name of an equivalent unit (1000 small calories) not a synonym.-->" This is contradicted by

• The cited source: "the amount of heat required to raise the temperature of one kilogram of water one degree Celsius that is equal to 1000 gram calories or 3.968 Btu—abbreviation Cal; called also kilocalorie" and "The calorie used by dietitians and food scientists and found on food labels is actually the kilocalorie (also called Calorie and abbreviated kcal or Cal), or 1,000 calories."[1]
• The article text that follows, viz, "This is exactly 1,000 small calories"

The argument above that it is not a common unit is flatly contradicted by the fact that it is used no less than four more times in the following paragraph, and was previously not defined. The time for scientific pedantry is when people muddle the calorie and the kilocalorie, not when you think that a heating a thousand grams of water is different to heating a kilogram of water. --Nigelj (talk) 21:59, 1 February 2013 (UTC)

There is no contradiction in the text "This is exactly 1,000 small calories". A kilolitre is exactly one cubic metre but this doesn't make kilolitre a synonym for cubic metre. A kilolitre is one thousand litres; a cubic metre is a metre times a metre times a metre. Equivalence and synonymy is not the same thing. The bar for inclusion is not truth but verifiability and these dictionaries fly in the face of the logic I set out above. Dictionaries can get things wrong though; here's one, for example, which says mammals don't lay eggs. I'm suggesting that we can do better than regurgitate this error. Here's a source (the BIMP) which defines the prefix kilo-. If kilo- means 1000, is kilocalorie not kilo- + calorie?There was no argument above that it is not a common unit. Is was a question as to whether it really was that common a unit in science. I don't believe that it is that common a unit in science. Certainly it may be common in the following paragraph but I was asking about science. But, okay, perhaps is should have been defined (for those unfamiliar with how metric prefixes work). I should be defined as 1000 small calories. JIMp _talk·cont 02:27, 9 February 2013 (UTC)

I have no idea what kind of WP:POINT you're trying to make here. --Nigelj (talk) 13:21, 9 February 2013 (UTC)

I'm afraid I have no idea what kind of a point you're trying to make with the link to Do not disrupt Wikipedia to illustrate a point. Would you be so kind as to explain the relationship between the current discussion and the advice given on that page? JIMp _talk·cont 05:30, 10 February 2013 (UTC)

The definition sounds odd (if not outright wrong) to me: A calorie is defined as the energy to heat 1 g water by 1 K. A kilocalorie is simply 1000 cal, thats precisely what the kilo prefix means, and I can't see how that constitutes "two classes". It would be interesting to have in the article a mention of where and when the usage of Calorie for kilocalorie was adopted, as it seems to be the root of much confusion. I have added kcal to the article. --Lasse Hillerøe Petersen (talk) 13:49, 13 February 2013 (UTC)

No, the calorie is not simply defined as the energy to heat 1 g water by 1 K. There are a multitude of definitions. Firstly, the amount of energy it takes to heat a given amount of water by 1 K depends on the initial temperature of the water. Secondly, the amount of energy also depends on how much water we've got. It's no good arguing that the proper amount is 1 g because some definitions use 1 kg. In fact the original definition used 1 kg. The root of the confusion was the adoption of the usage of "Calorie for kilocalorie" but of calorie for "milliCalorie". However, you're right that a history of this would be helpful. It's also true that 1 kcal is simply 1,000 cal, like you say, it can't help but be since "kilo" means 1,000. JIMp _talk·cont 09:08, 7 April 2013 (UTC)

It takes 1,000 times the energy to heat one kilogram of water through 1 °C as it takes to heat one gram through the same. It just must be the case, it's just obvious, it's a fact, right? Yes, it's a fact, like evolution, but not a deductive truth. We cannot know this a priori; it's a scientific fact. We have two different situations, one with a kilogram of water, the other with a gram; we theorise that it should take 1,000 time as much energy to heat the kilogram as it takes to heat the gram through 1 °C and find that this is what we observe. However, it's conceivable that it could have been otherwise, and even that it actually is otherwise and our measurements are off (perhaps not precise enough). Suppose we defined the while as the amount of time it takes to drink a jug of beer, could I manage to drink 1,000 jugs in a kilowhile? Suppose a pile is the amount of wood it takes to built a one-storey house, could I built a 100-storey tower with a hectopile? Suppose the schmile is the number of jokes it takes to make a person laugh, do I have to tell a kiloschmile to get a crowd of 1,000 laughing? Sure, heat doesn't work like this but we know this through experiment. One kilogram-calorie is the energy taken to heat one kilogram by 1 °C. One gram-kilocalorie is one thousand times the energy taken to heat one gram by 1 °C. That these are equivalent is just a function of how the Universe works but the fact remains that the definitions are not the same. The term kilocalorie is no just another name for the large calorie. JIMp _talk·cont 04:53, 19 April 2013 (UTC)