Talk:Conversion of units

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[edit] Don't Suppress Entries

Before we go off suppressing entries, let's make something clear: this table should be as exhaustive and self-contained as possible. If units are to be removed or moved to a separate table, let's include a link!

Urhixidur 13:53, 2004 Jun 23 (UTC)

[edit] Imperial?

I read "Imperial mechanical" and "Imperial electrical" (in Power->horsepower, for example) and have no idea of what does it mean, nor where to look it up. Please insert a link there or make an acclaration somewhere. — Euyyn 12:19, Aug 31, 2004 (UTC)

Patience, we're working on it. The SI units are nearly done, we'll get the Imperial system into shape next. The adjectives serve to put the unit in its system context. Imperial horsepower units are (or were) used in the Commonwealth countries because they were part of the British Empire in the past. Electrical horsepower is used in the electricity industry (to rate turbines, for example), whereas mechanical horsepower is used by engineers with machinery and engines (internal combustion or steam).
Urhixidur 12:49, 2004 Aug 31 (UTC)
Thanks! =) --euyyn 01:07, 12 Sep 2004 (UTC)

[edit] Alphabetical order

Should the units be in alphabetical order?

[edit] Relation to SI units

The litre is not an SI unit. The SI unit of volume is m³. Yet the column titled 'Relation to SI units' contains litre values. What do people think should be done?

The Litre may not be a "true" SI unit but it is "in use with it" (Système international d'unités (SI) 7ème édition (1998)). It has a simple power-of-ten relation to the cubic metre (unlike the hour and day), so it doesn't obscure the underlying value. I don't think we would gain much in converting all L to dm³, all mL to cm³, all μL to mm³. It wouldn't hurt, on the other hand. To sum up: I don't really object, but I won't do it myself.  :-)

Urhixidur 12:58, 2004 Oct 24 (UTC)

[edit] Dunams

Someone should include the Dunam in the Area section. Just to be really complete.:-) I would, but my concept of math and such is poor. --Penta 02:36, 27 Oct 2004 (UTC)

[edit] Natural units

Maybe we should add in conversions to natural units, or even a column. Because natural units are indeed the only truly cosmological constant units we have. That sounds important enought to warrant an entry, or even to warrant a column (since they're much more cosmological that say SI units). GWC Autumn 57 2004 13.30 EST

[edit] Different kinds of feet

Is it really true that there are five definitions of the "foot" (the normal one, Sear's, Indian, Benoît, and U.S. Survey) that differ among themselves by only +/- 0.6 microns? Do we have references for all these? --P3d0 16:01, Dec 24, 2004 (UTC)

Foot (British 1865) J. S. Clark's value of 0,304800837 metres (A. G. Bomford, "The Re-adjustment of the Indian Triangulation", Survey of India Professional Paper 28; 1939)
Foot (U.S. Survey; American) (Kasson) Metric Act of 1866 (Public Law 39-183) defines 1 m = 39,37 in exactly
Foot (Benoît) Jean-René Benoît (1841?-1915?) gives the 1895 British yard-metre ratio as 39,370113 inches per metre (or 0,9143992 metres per yard). Used in West Malaysian mapping. Refs: A. Guy Bomford (1899-1996), "Geodesy", 2nd edition 1962; after J. S. Clark, "Remeasurement of the Old 10-ft. Length Standards of the Ordnance Survey"; Empire Survey Review no. 90; 1953) Michelson, Albert Abraham & Benoît, Jean-René, 1895, Détermination expérimentale de la valeur du mètre en longueurs d’ondes lumineuses, Bureau international des poids et mesures, Travails et Mémoires 11, 1.
Foot (Indian) 0,99999566 British feet (A. R. Clarke 1865). British foot taken to be J. S. Clark's value of 0,304800837 metres (A. G. Bomford, "The Re-adjustment of the Indian Triangulation", Survey of India Professional Paper 28; 1939)
Foot (Sears) Sear's 1922-1926 British yard-metre ratio as given by Bomford as 39,370147 inches per metre (A. G. Bomford, "Geodesy", 2nd edition 1962; after J. S. Clark, "Remeasurement of the Old 10-ft. Length Standards of the Ordnance Survey"; Empire Survey Review no. 90; 1953); also given as 1 ft = 0,30479947 m (Australian Land Information Group http://www.ga.gov.au/nmd/geodesy/datums/history.jsp)
Foot (Clarke's; Cape; South African Geodetic) Alexander Ross Clarke's (1828-1914) 1858-1865 ratio of 1 British foot = 0,3047972654 French legal metres. Used in older Australian, Southern African & British West Indian mapping. (Australian Land Information Group http://www.ga.gov.au/nmd/geodesy/datums/history.jsp; see also J. S. Clark, "Remeasurement of the Old 10-ft. Length Standards of the Ordnance Survey"; Empire Survey Review no. 90; 1953)
Urhixidur 18:17, 2004 Dec 24 (UTC)
Uh... Wow. --P3d0 20:37, Dec 24, 2004 (UTC)
The only feet still in use nowadays are the "international foot" (the usual foot of 12 times 2.54 cm) and the U.S. Survey Foot. The others are historical curiosities now.
Urhixidur 05:42, 2004 Dec 25 (UTC)
No, the U.S. Ac of July 28, 1866 did not redefine the foot. The U.S. Treasury department had, back in 1832, defined the standard yard as
"the 36 inches between the 27th and 63d inches on a certain brass bar, commmonly designated as an 82-inch bar, prepared for the Coast Survey by Troughton of London. Hassler had brought this bar to the United States in 1815, after he had been detained in Europe for several years by the War of 1812. The 36-inch space referred to was supposed to be identical with the English standard at 62 °F, although it had never been directly compared with that standard.
"It is evident from Hassler's reports that he regarded the English yard as the real standard of length of the United States and the Troughton scale merely as a copy whose length should be corrected if it ws subsequently found to differ from the English yard; and this view was taken by others who subsequently had charge of the standards, as will be shown later on."
U.S. National Bureau of Standards, Weights and Measures Standards of the United States: a brief history, NBS Special Publication 447, orig. iss. Oct 1963, updated Mar 1976, p. 6
That remained the situation in the United States until the Mendenhall Order of 5 Apr 1893 redefined the yard as 3600/3937 meter. Ibid., pp. 16-17
The Act of July 28, 1866 only provided approximate conversion factors. It did not claim to redefine the foot or any other unit. (As far as intent of Congress goes, I would think that a certain number of Congressmen probably thought that this law "defined" the metric units, and that none of them thought it "defined" the customary units.) But the main thing is that this statute was not internally consistent enough to serve as definitions. Why would you pick the conversion factor 1 m = 39.37 as a definition, rather than the other conversion factors given there? It also said a myriameter equals 6.2137 miles (corresponding to a meter of 39.3700032 in), and that a millimeter equals 0.0394 in (1 m = 39.4 in). It did not mention yards in the length section (yards are the units primarily defined in both the Mendenhall order of 1893 and the Federal Register Notice of July 1, 1959 giving the current definition). In addition, the given conversion factors for gallons, bushels, cubin inches, fluid drams, and acres, square yards, and square inches, would result in several other slightly varying definitions of the foot, if these were indeed intended to be definitions. Gene Nygaard 05:35, 27 Dec 2004 (UTC)
I erred in citing the 1866 law for the U.S. Survey foot; according to NIST Special Publication 811, it is the 1893 definition that is used.
Urhixidur 00:18, 2005 Jan 3 (UTC)

The article currently lists just "foot" for the international foot and "foot (American; U.S. Survey)" for the US Survey foot. I think this could confuse a person who was not well-read about US surveying to think that the later version of the foot is used for all purposes in America. I suggest changing the US survey foot entry to foot (U.S. Survey). --Gerry Ashton 19:39, 31 July 2006 (UTC)

In the absence of an objection, I will change the entry as described above. --Gerry Ashton

[edit] Article bloat

I think it is time to discuss and try to reach some consensus on the scope of this article. I'll throw out some of my suggestions to get the ball rolling. For example, when editing it we get a message about trying to restrict it to 32 kilobytes, and we could easily do so.

If nobody cares enough to discuss it, I'll just start editing in accordance with these principles.

  • This article should only list units which have seen some significant use in the 20th century or later, at least in some geographical location or field of activity. Leave the rest to medieval weights and measures or ancient weights and measures.
    • In his 1790 report to the House of Representatives, Thomas Jefferson made this characterization:[1] "coomb, dry; this last term being ancient and little used." This unit has seen no revival since then.
  • There is no need to list every variant definition in use.
    • Yes or no?
      • The difference between imperial gallons and U.S. liquid gallons, yes.
      • The difference between the international foot and the 1893-1959 U.S. foot still used in USGS surveys, debatable.
      • The difference between the Paris pied (foot) and the Quebec pied, definitely not. In this case, neither unit has been used before the 20th century, so I'd say they don't belong here at all.
    • Include one or two identified variants of the Btu and the calorie; leave the rarely used ones to the respecive articles on the units.
  • There is no need to list every historical variation in the definitions. Leave that to the specific article on that unit.
    • The distinction made here between torrs and millimetres of mercury is silly. Both names are used now with the definition listed under torr; both names were used in the past with the older definition listed under millimetre of mercury. Combine both names under the current definition.
  • When compound units include a component of time, volume, or area, there is no need to list every possible combination of hours, minutes, seconds, years, etc.; nor every Cubic centimetre, millilitre, cubic millimetre, decilitre, cubic metre, etc. Pick the ones in common use; forget the others.

Gene Nygaard 19:16, 2 Jan 2005 (UTC)

I agree that a lot of conversion factors could/should be pushed out to the relevant articles (e.g. the various feet). Key variants such as the U.S. vs Imperial values ought to be kept, that is obvious. So should the U.S. Survey units —at the very least the mile ("statute mile"). The distinction between torr and mmHg may seem silly to some, but is nevertheless real.

The problem with paring the list down, farming sublists out to articles, and so on, is that one then no longer has the convenient master list in one place. If we're worried mostly about the list's size, the first step should be to make each section into a separate page (e.g. "Conversion of units (Volume)" and so on). Similarly, removing some divisions (per minute, per hour, per day, etc.) for convenience's sake is no good —one user's most frequently used magnitude won't match another, depending on context. Flow rates in oceanography won't be in the same ranges as flow rates for home air infiltration measurements, for example. In that sense, "common use" is not definable.

Urhixidur 00:13, 2005 Jan 3 (UTC)

There are not two different units called "torr" and "millimeter of mercury". There is an older definition for this unit under either name based on a conventional density of mercury at 0 °C, and there is the current definition of this unit under either name as 1/760 of a standard atmosphere defined as 101.325 kPa. Torr and mmHg only have one joint Wikipedia article, and quite properly so. Historical variations can be dealt with on that page, just like no-longer-used definitions of feet.
Most of what I'm talking about should not be "farmed out"; some could be made clearer in the individual articles linked to here.
I have no problem with flow rates or various other combinations of units actually used to some significant extent. Many of them listed here are not.
This article is linked to from other articles to provide guidance in making conversions from units that might be encountered in that context, and as a reference source for those Wikipedia editors trying to add conversions to measurements already existing in other articles.
It doesn't need to be cluttered up with useless things such as inches and leagues based on the U.S. survey foot, which are never used.
It doesn't need every historical variation in different units.
Things which are not units of measurement
  • It doesn't need trivia like various multiples of wine bottle sizes, never used as "units of measurement" as such but only as particular standard sizes, and furthermore which varied in size depending on the size of the prevailing "standard bottle" (now 750 mL, not the size used here).
  • Other things never actually used as "units of measure" include "link (Ramden's, Engineer's)" where link can be used to refer to a physical part of the measuring device, but the results of the measurement are expressed in "feet"—units already listed here and readily available for conversion. Whenever "link" and "chain" are used as units of measurement, it is a virtual certainty that it is "Gunter's chain" that is referred to. There is absolutely no ambiguity to worry about.
Gene Nygaard 16:38, 26 Jan 2005 (UTC)

[edit] Correct conversion to coulombs?

What is the correct conversion factor from faradays to coulombs? Faraday says 96485.3415, but conversion of units says 96485.3383. Is either one of these an "accepted" conversion value? (message posted to Talk:Faraday and Talk:Conversion of units.) --bdesham 13:58, 8 Apr 2005 (UTC)

I would guess that it depends on the actual definition of those Fred Flintstone units (faradays) which is being used, something that is time-dependent and field-of-activity-dependent. Do you remember the days when faradays were still used, and when physicists defined atomic weight differently from the way chemists defined it, when both were different from the current unified atomic mass unit? Gene Nygaard 14:05, 8 Apr 2005 (UTC)
No, I'm far too young for that :-) In any event, though, the article(s) should be changed to reflect the potential differences in the definition of the faraday—I'd do it myself, but obviously, I don't know enough to do that. --bdesham 18:56, 8 Apr 2005 (UTC)

[edit] Light Year?

Is there an official definition of a light-year anywhere? Whoever supplied the figure listed here apparantly used a Julian year. Is it really officially defined as such, or is it not a formally-defined unit?

I don’t know how official that value is, but it is in accordance to the main article: light year. Christoph Päper 18:42, 6 March 2006 (UTC)

[edit] Exact/Defined Formatting

I think splitting the "Relation to SI Units" columns into "Definition" and "SI Equivilency" or something to that effect would make the mess of numbers much clearer. I can do this if there is no objection. Prometheus235 18:58, 16 Jun 2005 (UTC)

Kudos to User:Crissov for doing the def. column. I tried to polish up the length table to make it more intuitive between exact, defined, and approx. quantites, here's the first bit of it:
Key:
  • () Repeated digits, e.g. 1/11 = 0.09(09)
  • Bold Exact quantities
Length, l
Name of unit Symbol Definition SI equivalent
metre (SI base unit) m co × (1/299 792 458) s 1 m
inch in, " 2.54×10-2 m
fermi, femtometre fm 10-15 m 10-15 m
x unit; siegbahn xu 1.0021×10-13 m
stigma, picometre pm 10-12 m 10-12 m
Bohr radius; atomic unit of length a0, b; au α/(4πR∞) 5.291 772 083×10-11 ± 19×10-20 m
ångström Å 10-10 m 10-10 m
micrometre, micron µ, µm 10-6 m 10-6 m
twip twp 1/1440 in 1.763 (8)×10-5 m
mil; thou mil 10-3 in 2.54×10-5 m
mickey   1/200 in 1.27×10-4 m
point (ATA) pt 0.013837 in 3.514 598×10-4 m
point (PostScript) pt 1/72 in 3.52(7)×10-4 m
point (metric) pt 3/8 mm 3.75×10-4 m
point (Didot; European) pt 1/72 French royal inch 3.759 715×10-4 m
I more or less removed superfluous digits, converted it all to meters w/ sci. notation, filled in definitions, etc. I'd like some feedback before I go and do everything. -- Prometheus235 21:04, 20 Jun 2005 (UTC)
I prefer engineer style, x·103·n, but scientific style should be fine. I also prefer · over ×, but × seems to be more common in English usage. Equals sign etc. have an advantage when copying to plain text. Christoph Päper 21:54, 20 Jun 2005 (UTC)
I'd actually prefer the ˙ and eng notation (for some quantities), but × seems to be more prevelant in WP. I'm trying to move away from all the equals, approx, equivalent to signs because they are generally confusing, as far as copying into plaintext it doesn't seems that important, most users would probably only be interested in one of the quantities so wouldn't mind a missing sign. I'd also like to sort the units differently, so users wouldn't have to sift through the dozens of obscure units to find a more common one, however I'm not exactly sure how. -- Prometheus235 23:20, 20 Jun 2005 (UTC)

[edit] Planck time

Hey, according to this table, a Planck time is defined as: rt(Gh/c^5), where h is a Planck constant. According to the page, it is rt(Gh-bar/c^5), where h-bar is a reduced Planck constant, h/2π. I'm assuming the second one is correct, so I'll change it to that. However, I don't know how to make an hbar without using math tags, which screw up the table. Now the only way I can show that the h is a Dirac's constant, not a Planck constant, is by making the h link to Dirac's constant, which redirects to... Planck's constant. Quite annoying. If anyone can make an hbar that works here, it'd be appreciated. --Dyss 2 July 2005 21:12 (UTC)


Thanks for all your incredible work here. I have, however, noticed a discrepancy in the measure of Planck time. On this table it is equated with SI units as: 1.351 211 818×10^-43 s.

However, on a related wiki page, [2], the measure is: 5.391 x 10^-44. [--207.30.168.9 23:26, 8 November 2005 (UTC) - Karl Kaiser]

[edit] Link to "sign"

In the table "Angle", I have removed the link on the word "sign", because it pointed to an article about positive and negative numbers. Couldn't find an appropriate page to link it to. Iggle 07:21, 29 March 2006 (UTC)

[edit] Candela, Lumen and Lux

An anon asked on the article page about these units. The El Reyko 20:35, 6 April 2006 (UTC)

[edit] templates

I made some templates for conversion, see {{fahrenheit}}, {{inch}} and {{fluid ounce}}. →AzaToth 21:04, 13 April 2006 (UTC)

[edit] Postscript Points

The table lists a postscript point as being 1/72in. I don't think this is the case. I agree that much documentation lists a point as being 1/72in, but in my experiments, I believe the postscript interpreter uses 1/72.27, which is the ATA point. -- Ch'marr 23:40, 23 April 2006 (UTC)

Nevermind. I should research before shooting my mouth off :) -- Ch'marr 23:50, 23 April 2006 (UTC)

[edit] Radiation?

I was looking up fatal doses of radiation the other day, and it occured to me that there are several different kinds of ways to measure radiation. Off the top of my head I can think of rems, rads, grays, and roentgens. Should a section be made to include in this article?

[edit] Discuss links here

Editors regularly clean out undiscussed links from this article. Please discuss here if you want a link not to be cleaned out regularly. (You can help!)

I start this section because I fully agree with the recent cleanup edit. This article is not a Web directory to online converters. If there are specific reasons to include particular links, please provide them here first. Femto 17:54, 29 May 2006 (UTC)

Hi, I posted the following link: http://publicliterature.org/tools/unit_conversion/

It helped me do a college project very well. It's got units from many fields. Please consider it as a regular link.—The preceding unsigned comment was added by 69.140.31.81 (talk • contribs) .

Should be avoided as an external link (WP:EL). All I got is a page with code for Google ads and a Shockwave Flash application that I won't run on my system. Generally, I don't think this article can benefit from external conversion services. Femto 11:50, 9 June 2006 (UTC)
I just removed a bunch of these from individual unit articles like kilometre. I though maybe one such link might belong on this page, if any, but I think I agree with you. —johndburger 19:16, 9 June 2006 (UTC)

I put in Unicalc Live web calculator doing units conversion by dimensional analysis as this is a powerful and easy to use tool I use all the time. Your mileage may vary. Jim Bowery 19:02, 3 July 2006 (UTC)

Please read Wikipedia:External links, and then explain why this link belongs here. In what way does the calculator add to a reader's understanding of the topic, over and above the article and the other external links? It may be a great site, it may be in the same topic area as the article, but that does not mean it is a good external link. —johndburger 02:38, 4 July 2006 (UTC)
"Sites that contain neutral and accurate material not already in the article. Ideally this content should be integrated into the Wikipedia article, then the link would remain as a reference, but in some cases this is not possible for copyright reasons or because 'the site has a level of detail which is inappropriate for the Wikipedia article. Sites with other meaningful, relevant content that is not suitable for inclusion in an article, such as textbooks." Jim Bowery 20:03, 4 July 2006 (UTC)
Where does the "content" come in here? Femto 11:37, 7 July 2006 (UTC)
That was my (perhaps too subtle) point—there is little, if any, actual content on that site at all, unless you count "60 kph = 100215 furlonghs/fortnight" and the like. So it seems to me it's completely ineligible as an external link, at least for this article. —johndburger 01:50, 8 July 2006 (UTC)

I believe http://www.unitconversion.org should be featured in the external links section since it is the only site to support correct conversions between units - besides it is ads free. —The preceding unsigned comment was added by 195.131.172.165 (talk • contribs) .

Hm, I'm prompted to install a demo version right there, not what I'd call completely ads free... As soon as the first external conversion service link gets allowed, there'll follow a rat tail of spamlinks which someone feels at least as worthy of inclusion. The history of this section shows that everybody has their own favorite. It's a purely subjective decision, and WP's external links are not a popularity-based Web directory. We can't add all, so there is none. A solution could be to include one link only, to an open Web directory on these conversion tools, as suggested by WP:EL. Femto 11:37, 7 July 2006 (UTC)
you are completely off here - the site offers all the converters for FREE. it is unmatched with any others in the list - just dig futher. the _site_ is ad free

its very handy and way forward of any others online javascript converters

I would like to add a link to http://www.converzions.com

converZions is an extensive unit conversion site that can answer conversion related question such as: 'How many kilograms are in ten pounds?' I believe it will be a useful resource for the readers of this article. Please approve. —The preceding unsigned comment was added by 67.80.55.108 (talk • contribs) .

Rather not, see my reasonings above. Femto 12:55, 28 July 2006 (UTC)

[edit] Javascript Converter

Do we want to make a javascript unit converter part of wikipedia? --RobBrisbane 00:45, 13 June 2006 (UTC)

[edit] all the numbers you get after performing calculations on a calculator or with pencil and paper are not meaningful.

What does this mean? Is it - a) not all the numbers you get are meaningful, or b) all the numbers you get are meaningless.

TharkunColl 23:04, 13 June 2006 (UTC)

[edit] Reference section added

A change was made today, redefining a line from 1/12 to 1/16 inch. I changed it back, and added a reference section so we can show where we obtained information on the more obscure units. I used Harvard style references rather than the usual <ref> tags because the raised reference numbers caused by <ref> tags could be mistaken for exponents in this context. --Gerry Ashton 01:46, 13 August 2006 (UTC)

[edit] Zentner

An editor using the IP address 87.160.227.58 claims a Zentner is 50 kg rather than 100 kg. I have reverted this change because no citation was provided to prove the claim. --Gerry Ashton 19:18, 14 October 2006 (UTC)

The second hit googling zentner is this. Looks like there are at least two meanings. -- Bpmullins 19:58, 14 October 2006 (UTC)
Thanks for adding that to the table, Garry. I'd have done it, but I wasn't sure of how to format it and hadn't had a chance to fiddle around.
I think the anon editor was correct that the Zentner is always 50 kg - see the discussion here. Cheers -- Bpmullins 21:13, 14 October 2006 (UTC)
That discussion appears to have come from the British Weights and Measures Association, an anti-metric advocacy group, so that just isn't a reliable source and I give it no weight. --Gerry Ashton 22:00, 14 October 2006 (UTC)
Okay, I see your point there. However, 'zent' seems cognate to 'cent'=100, and as a traditional measure it wouldn't have meant 100 kg. Or so it looks to me. I'll continue digging... -- Bpmullins 15:29, 15 October 2006 (UTC)
I hope you noticed the footnote indicating that the 100 kg meaning comes from the Swiss Federal Office for Metrology website. I have no way to know whether it might have meant 100 Swiss pounds before it meant 100 kg, and I have no way to know whether the Swiss actually pay any attention to their Office for Metrology. The only thing I'm sure of is I'll never use the Zentner, and if anyone sends me a document using it, I'll reject the document and demand it be rewritten in SI units. --Gerry Ashton 16:55, 15 October 2006 (UTC)

Like the English hundredweight (and similar quintal/centner) the German Zentner used to mean one hundred pounds (Pfund), but just like the English one that didn't always mean 100, but for example in 19th-century Prussia it was 110 Pfund. With the metrication during Napoleonic occupation and the process of German unification until 1871 some traditional units had been given round metric values and, most importantly, these were the same nation-wide. This included most prominently the Pfund of 500 g, which made the Zentner 50 kg without a change in its base definition of 100 Pfund. (Other examples are the Scheffel (German bushel) of 50 l and the Morgen (German acre) of 25 a.) Austria(-Hungary) was finally not part of the new German Empire and so maybe the differing definition of 100 kg evolved. Switzerland (like perhaps some Southern states like Baden) already had the French quintal of 100 kg and Zentner is actually just the German word for that, so they went with this deciton value, which was called Doppelzentner (i.e. "double centner") in the North. Some sources list Meterzentner, which is just an optional distinguishing term like "short hundredweight", "metric ton" or "Neu-Scheffel". The articles quintal and de:Zentner provide most or all of this information. There's a myriad of "metric" units like this one, should they all be included, recognising that most of them are outdated and merely colloquial today? Christoph Päper 12:07, 18 October 2006 (UTC)

Thanks for the information. With such a complicated history, a unit like this won't fit comfortably in tabular format. Maybe we should just provide a link to the relevant articles? -- Bpmullins 16:24, 18 October 2006 (UTC)
When this series of edits began, the Zentner article was totally unsourced. It is somewhat better now, although still weak on sources. Still, I think the best solution is to not give a value in the table and instead provide some kind of link or note, along the lines of "Definitions vary, seek clarification from source." --Gerry Ashton 18:04, 18 October 2006 (UTC)
I emailed the author of the source in Bpmullins' first post to this discussion and here is his reply to me:

The zentner is the German "hundredweight"; it originally meant 100 pfund but usually means 100 kg today. The same considerations apply to other European hundredweight measures such as the quintal. This is a particular egregious example of a common problem: any table of equivalents of units is time dependent, because definitions of units change over time. If you're building a table of current equivalents, then 100 kg is a zentner. If you're more interested in early 20th century units, then it's 50 kg, and if you're interested in 19th century units its 100 (or maybe 110) pfund.

Russ Rowlett
University of North Carolina
Chapel Hill NC USA
So, basically in order to define it, you would have to qualify what time period the zentner is from—19th century, early 20th century, or present.—MJCdetroit 15:12, 19 October 2006 (UTC)
I’m sorry, but Mr. Rowlett’s information is erroneous. The Zentner is still considered 50 kg in most if not all parts of Germany. (The notion of a 100-kg definition had been repeatedly removed from the article in the German WP, probably because people thought that part had to be wrong, because they never heard of this definition that differs from their experience. Austrian and Swiss users are minorities.) This is also the only federal definition there ever has been. There are, however, increasingly more people not familiar with the unit at all, who might assume it to be 100 kg. I don’t know much about comparable processes in other European countries.
He is of course right in pointing out that units may have their definitions changed over time, and be it just for higher precision. Christoph Päper 21:04, 21 October 2006 (UTC)

[edit] information enthropy SI unit for information enthropy = J/K???

This one looks really weird to me. It's quite possible that it's a correct unit, but deriving information entropy from energy and temperature looks really weird to me (as either concept not really is a core concept in information theory, however information entropy is). On the other hand, someone found really neat looking conversion factors, and there are relations between information theory and thermodynamics, what is where the unit really looks to belong. So, what I request is a reference for more information on this topic, to learn more about it. Also, information entropy should be extended with this info. TERdON 14:03, 3 January 2007 (UTC)


Is the 7.839695(13) × 10−23 J/K for byte in the information entropy correct, i think the -23 in the exponent should be -20, 7.839695(13) × 10−20 J/K.

[edit] US Gallons / US Fluid Ounce

In other articles the US Fluid Ounce is defined as 1/128 of one US Gallon. However given the conversion factors in this article (1 US Gallon) / (1 US Fluid Ounce) = 133.2278695406382. Why is this? OlJanx 05:17, 3 February 2007 (UTC)

Please provide some search text so we can find which line in the table you are writing about. --Gerry Ashton 05:42, 3 February 2007 (UTC)
The following are lines from the Volume table:
fluid ounce (U.S.) fl oz (US) ≡ 1/128 gal (US) = 29.573 529 562 5 mL
gallon (U.S. fluid; Wine) gal (US) ≡ 231 cu in = 3.785 411 784 L
The conversion between the two units can be done like this:
(3.785411784 L)/(.0295735295625 L) = 133.2278695406382
--67.165.215.241 21:47, 3 February 2007 (UTC)
When I do the calculation (3.785411784 L)/(.0295735295625 L) with a TI-36X calculator, I get the answer 128.0000024. Perhaps your calculator is not working properly due to the many digits; try entering shorter approximations into your calculator, such as 3.7854/0.02957 and see if you get an answer close to 128. --Gerry Ashton 22:00, 3 February 2007 (UTC)
I tested the above calculation on a TI-84 and got the answer 128. The error was apparently a typo on my part. I apologize for not properly testing the issue before bringing it up in this discussion. --OlJanx 07:38, 4 February 2007 (UTC)

[edit] Should this article be a list?

This article seems that it should be an explanation of what conversion of units is and how to do it, not a list of conversion of units. Maybe we should start another article that could be something like common unit conversions. Also, Software tools is at the end of the page, after the table, that should at least come before it, so that its actual will be read. Finally, mass has an empty column "relation to avoirdupois," which as I understand it is the English weight system. Either we should have Imperial units in there, or not, but we shouldn't have an empty column.Markid 04:36, 1 March 2007 (UTC)

[edit] List of unit converters?

Well, just a suggestion. But would it not be an idea to list some free unit converters in external links?

e.g. http://library.thinkquest.org/11771/english/hi/chemistry/convert.shtml http://www.micro-sys.dk/services/unit-convert/ http://www.convert-me.com etc. —The preceding unsigned comment was added by 83.88.199.154 (talk) 11:59, 12 March 2007 (UTC).

[edit] Mach speed

Should this be added to the list? I know that it varies from temperature and air volume. Thanks, user:marasama 3/25/07.

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