# Apart from decibels, are there any other metric units that are only ever used with a single prefix? **URL:** \ **Category:** Factual Questions\ **Created:** [June 13, 2020, 2:29pm UTC](https://boards.straightdope.com/t/apart-from-decibels-are-there-any-other-metric-units-that-are-only-ever-used-with-a-single-prefix/855604 "2020-06-13T14:29:54Z")\ **Posts on this page:** 20\ **Page:** 4
**Author:** ![Schnitte](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/schnitte/32/9033_2.png) [@Schnitte](https://boards.straightdope.com/u/Schnitte)\ **Post date:** [June 15, 2020, 2:46pm UTC](https://boards.straightdope.com/t/apart-from-decibels-are-there-any-other-metric-units-that-are-only-ever-used-with-a-single-prefix/855604/61 "2020-06-15T14:46:58Z")
> [@jz78817](#): > > I was somewhat amused when I looked at a label in the cargo area of a EU-market Ford Transit van which indicated some sort of capacity in “daN” (decaNewtons.) I looked into it a bit more and that was evidently the “lashing” capacity; i.e. the rated force the cargo hold-downs could take. surprised me that daN is a common measure for LC. Interesting, never heard of that. Part of the reason could be that a deca-Newton is very close to the weight of a kilogram of mass in Earth’s gravity. ---
**Author:** ![ZipperJJ](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zipperjj/32/211_2.png) [@ZipperJJ](https://boards.straightdope.com/u/ZipperJJ)\ **Post date:** [June 15, 2020, 2:54pm UTC](https://boards.straightdope.com/t/apart-from-decibels-are-there-any-other-metric-units-that-are-only-ever-used-with-a-single-prefix/855604/62 "2020-06-15T14:54:04Z")
> [@Colibri](#): > > The milli-Helen is the unit of beauty sufficient to launch one ship. I have never heard of any other prefix used with Helens. [30 Helens](https://www.youtube.com/watch?v=qCxbQADotrw) is a KITH 😉 ---
**Author:** ![excavating\_for\_a\_mind](https://avatars.discourse-cdn.com/v4/letter/e/e8c25b/32.png) [@excavating\_for\_a\_mind](https://boards.straightdope.com/u/excavating_for_a_mind)\ **Post date:** [June 15, 2020, 3:20pm UTC](https://boards.straightdope.com/t/apart-from-decibels-are-there-any-other-metric-units-that-are-only-ever-used-with-a-single-prefix/855604/63 "2020-06-15T15:20:09Z")
While we’re on the subject of decibels (or, to get back to it), why is the standard unit a _deci_bel, and not just a bel? When I was in grade school, they told me that one bel was such a large difference in loudness that they typically use decibel as the standard unit. But, is that really important? [According to this site](https://www.tlc-direct.co.uk/Technical/Sounds/Decibles.htm) one bell is approximately the sound of someone breathing. Normal conversation is about 5-6.5 bels. City traffic around 8 bels. Continuous exposure to levels above 9 bels can lead to hearing loss. Perhaps the real reason is that bel sounds a lot like bell (perhaps, exactly like), and the phrase “as loud as a bell” (to indicate loud and clear) could get confused with “as loud as a bel” (which would be very quiet). ---
**Author:** ![jz78817](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jz78817/32/1028_2.png) [@jz78817](https://boards.straightdope.com/u/jz78817)\ **Post date:** [June 15, 2020, 3:31pm UTC](https://boards.straightdope.com/t/apart-from-decibels-are-there-any-other-metric-units-that-are-only-ever-used-with-a-single-prefix/855604/64 "2020-06-15T15:31:34Z")
> [@excavating\_for\_a\_mind](#): > > While we’re on the subject of decibels (or, to get back to it), why is the standard unit a _deci_bel, and not just a bel? When I was in grade school, they told me that one bel was such a large difference in loudness that they typically use decibel as the standard unit. But, is that really important? [According to this site](https://www.tlc-direct.co.uk/Technical/Sounds/Decibles.htm) one bell is approximately the sound of someone breathing. Normal conversation is about 5-6.5 bels. City traffic around 8 bels. Continuous exposure to levels above 9 bels can lead to hearing loss. > > Perhaps the real reason is that bel sounds a lot like bell (perhaps, exactly like), and the phrase “as loud as a bell” (to indicate loud and clear) could get confused with “as loud as a bel” (which would be very quiet). the unit was originally meant for measuring transmission loss in communications cable, not sound pressure. > **[Decibel | History](https://en.wikipedia.org/wiki/Decibel#History)** > > The decibel originates from methods used to quantify signal loss in telegraph and telephone circuits. Until the mid-1920s, the unit for loss was Miles of Standard Cable (MSC). 1 MSC corresponded to the loss of power over one mile (approximately 1.6 km) of standard telephone cable at a frequency of 5000 radians per second (795.8 Hz), and matched closely the smallest attenuation detectable to a listener. A standard telephone cable was "a cable having uniformly distributed resistance of 88 ohms per ... ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [June 15, 2020, 3:56pm UTC](https://boards.straightdope.com/t/apart-from-decibels-are-there-any-other-metric-units-that-are-only-ever-used-with-a-single-prefix/855604/65 "2020-06-15T15:56:39Z")
[duplicated] ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [June 15, 2020, 3:58pm UTC](https://boards.straightdope.com/t/apart-from-decibels-are-there-any-other-metric-units-that-are-only-ever-used-with-a-single-prefix/855604/66 "2020-06-15T15:58:20Z")
If you think of 1 bel = 10x power, that seems quite natural as a base unit, and is easy to remember. But, for practical engineering, people evidently found decibels more convenient, as 3 dB is already twice the power. It does have the effect that one rarely sees another, or no, prefix. Sort of like when people state the circumference of the Earth is 40000 km, rather than 40.0 Mm ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 15, 2020, 4:46pm UTC](https://boards.straightdope.com/t/apart-from-decibels-are-there-any-other-metric-units-that-are-only-ever-used-with-a-single-prefix/855604/67 "2020-06-15T16:46:29Z")
On the other hand, solar physicists frequently use Mm for describing the size of features on the surface of the Sun. ---
**Author:** ![Pancake\_Robot](https://avatars.discourse-cdn.com/v4/letter/p/f08c70/32.png) [@Pancake\_Robot](https://boards.straightdope.com/u/Pancake_Robot)\ **Post date:** [June 15, 2020, 5:57pm UTC](https://boards.straightdope.com/t/apart-from-decibels-are-there-any-other-metric-units-that-are-only-ever-used-with-a-single-prefix/855604/68 "2020-06-15T17:57:41Z")
> [@Colibri](#): > > The milli-Helen is the unit of beauty sufficient to launch one ship. I have never heard of any other prefix used with Helens. Thirty Helens Agree. ---
**Author:** ![Do\_Not\_Taunt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/do_not_taunt/32/2968_2.png) [@Do\_Not\_Taunt](https://boards.straightdope.com/u/Do_Not_Taunt)\ **Post date:** [June 15, 2020, 6:19pm UTC](https://boards.straightdope.com/t/apart-from-decibels-are-there-any-other-metric-units-that-are-only-ever-used-with-a-single-prefix/855604/69 "2020-06-15T18:19:41Z")
> [@racer72](#): > > My water bill in measured in cubic feet. Here, a couple dozen miles northwest of you, our water bill is measured in ccfs, or hundreds of cubic feet. Does yours really come with the increased precision? ---
**Author:** ![SirRay](https://avatars.discourse-cdn.com/v4/letter/s/cc9497/32.png) [@SirRay](https://boards.straightdope.com/u/SirRay)\ **Post date:** [June 15, 2020, 8:48pm UTC](https://boards.straightdope.com/t/apart-from-decibels-are-there-any-other-metric-units-that-are-only-ever-used-with-a-single-prefix/855604/70 "2020-06-15T20:48:13Z")
> [@Do\_Not\_Taunt](#): > > Here, a couple dozen miles northwest of you, our water bill is measured in ccfs, or hundreds of cubic feet. Does yours really come with the increased precision? Sadly, in the NY tri-state area our gas usage is measure in Therms, our water usage in Gallons, and land area in square feet (as evidenced by all the CBRE “For Lease” signs on our commercial real estate). Did we mention Centilitres for wine and other alcohol? I’m trying to think of electrical units that might meet the OP’s concept, but Farads, Henrys, Volts, Ohms, Siemens, Watts, Amperes, Gauss, Telsas, Coulombs and the like all seem to have powers of ten in practical usage (e.g. 2 kilo-ohm resistor, 10 ohms, 50 milli-ohms, etc) ---
**Author:** ![Tripler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripler/32/21807_2.png) [@Tripler](https://boards.straightdope.com/u/Tripler)\ **Post date:** [June 15, 2020, 10:02pm UTC](https://boards.straightdope.com/t/apart-from-decibels-are-there-any-other-metric-units-that-are-only-ever-used-with-a-single-prefix/855604/71 "2020-06-15T22:02:27Z")
> [@Colibri](#): > > The milli-Helen is the unit of beauty sufficient to launch one ship. I have never heard of any other prefix used with Helens. Several of us knew a guy in college, “Vern” who, to put it mildly, was _not_ gifted with attractive features. We collectively coined the unit of a **milliVern** as being so ugly you could stop a loaded semi-truck. We coined another unit on this board, based in part on the ugliness of another poster, but that’s another tale for another day. Tripler I think I’m one picoVern. Not too ugly, but I unfortunately make babies cry. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [June 16, 2020, 1:51am UTC](https://boards.straightdope.com/t/apart-from-decibels-are-there-any-other-metric-units-that-are-only-ever-used-with-a-single-prefix/855604/72 "2020-06-16T01:51:54Z")
In the field of medications, doses are always (that I’ve seen) measured in milligrams or micrograms, never in other multiples. Sometimes, doses are as large as thousands of milligrams (yes, whole grams) yet those doses are never described in grams. For examples, I had a Rx of amoxicillin tablets of 500 milligrams each, but these were not described as 0.5 grams. I have this here bottle of generic acetaminophen tablets of 500 milligrams each, also not described as being 0.5 grams. The instructions suggest taking two tablets (1000 milligrams) at a time up to a maximum of 2500 milligrams a day. These amounts are 1 whole gram and 2.5 grams, yet such doses are never written that way. Micrograms are a common unit of measure for inhaled medications. ---
**Author:** ![abcdefghij](https://avatars.discourse-cdn.com/v4/letter/a/43a26b/32.png) [@abcdefghij](https://boards.straightdope.com/u/abcdefghij)\ **Post date:** [June 16, 2020, 11:58pm UTC](https://boards.straightdope.com/t/apart-from-decibels-are-there-any-other-metric-units-that-are-only-ever-used-with-a-single-prefix/855604/74 "2020-06-16T23:58:19Z")
> [@Chronos](#): > > Nobody ever measures pressure in centimeters of mercury, or micrometers of mercury, or whatever. When I was in grad school, the instruction manual for our turbo pump said “do this until XXX microns, then do that until YYY microns”. It took a fair bit of head scratching before we figured out that they meant micrometers of mercury. ---
**Author:** ![abcdefghij](https://avatars.discourse-cdn.com/v4/letter/a/43a26b/32.png) [@abcdefghij](https://boards.straightdope.com/u/abcdefghij)\ **Post date:** [June 17, 2020, 12:18am UTC](https://boards.straightdope.com/t/apart-from-decibels-are-there-any-other-metric-units-that-are-only-ever-used-with-a-single-prefix/855604/75 "2020-06-17T00:18:43Z")
> [@abcdefghij](#): > > the instruction manual for our turbo pump said “do this until XXX microns, then do that until YYY microns” Clearly I should have read a bit further ---
**Author:** ![abcdefghij](https://avatars.discourse-cdn.com/v4/letter/a/43a26b/32.png) [@abcdefghij](https://boards.straightdope.com/u/abcdefghij)\ **Post date:** [June 17, 2020, 12:25am UTC](https://boards.straightdope.com/t/apart-from-decibels-are-there-any-other-metric-units-that-are-only-ever-used-with-a-single-prefix/855604/76 "2020-06-17T00:25:52Z")
> [@Schnitte](#): > > Ironically, the predecessor unit, the Curie (Ci), was suffering from the opposite problem: 1 Ci (equivalent to 37 GBq) was so much that it would often have to be prefixed with centi- or milli- prefixes. I was trained in the submarine service that the limit for surface contamination was 450 micromicroCuries per 100 cm^2, often known as “450 MickeyMikes”. I never did figure out what was wrong with 4.5 pCi / cm^2. A common joke was “What do you do if you frisk out of the reactor compartment with 1800 MickeyMikes on your hand? Wipe your hands together for 900. Wipe your hands on your pants for 450. You’re clean!” ---
**Author:** ![UltraVires](https://avatars.discourse-cdn.com/v4/letter/u/ecccb3/32.png) [@UltraVires](https://boards.straightdope.com/u/UltraVires)\ **Post date:** [June 17, 2020, 5:21am UTC](https://boards.straightdope.com/t/apart-from-decibels-are-there-any-other-metric-units-that-are-only-ever-used-with-a-single-prefix/855604/77 "2020-06-17T05:21:57Z")
> [@am77494](#): > > Degree is not used with Kelvin. > > “ The 13th CGPM changed the unit name to simply “kelvin” (symbol: K).[13] The omission of “degree” indicates that it is not relative to an arbitrary reference point like the Celsius and Fahrenheit scales ” > > [Kelvin - Wikipedia](https://en.m.wikipedia.org/wiki/Kelvin) I don’t understand. It has an arbitrary reference point: absolute zero. That might be a good starting point, but I don’t see how that is less arbitrary than the freezing point of water. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [June 17, 2020, 6:00am UTC](https://boards.straightdope.com/t/apart-from-decibels-are-there-any-other-metric-units-that-are-only-ever-used-with-a-single-prefix/855604/78 "2020-06-17T06:00:47Z")
> [@UltraVires](#): > > I don’t understand. It has an arbitrary reference point: absolute zero. That might be a good starting point, but I don’t see how that is less arbitrary than the freezing point of water. Absolute temperature is not arbitrary, though. It measures something, e.g., the ratio between internal energy (heat) and entropy change, the average kinetic energy of gas particles, etc. Absolute zero means something, but there is an arbitrary choice to make for the size of your temperature unit. Water comes into it merely as a reference point; in modern terms, Boltzmann’s constant is defined so that the triple point of water is what you would expect. ---
**Author:** ![Steven\_G](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/steven_g/32/5080_2.png) [@Steven\_G](https://boards.straightdope.com/u/Steven_G)\ **Post date:** [June 17, 2020, 1:04pm UTC](https://boards.straightdope.com/t/apart-from-decibels-are-there-any-other-metric-units-that-are-only-ever-used-with-a-single-prefix/855604/79 "2020-06-17T13:04:32Z")
> [@UltraVires](#): > > I don’t understand. It has an arbitrary reference point: absolute zero. That might be a good starting point, but I don’t see how that is less arbitrary than the freezing point of water. A couple of relevant definitions of Arbitrary: subject to individual will or judgment without restriction; contingent solely upon one’s discretion undetermined; not assigned a specific value And one for Absolute: something that is not dependent upon external conditions for existence or for its specific nature, size, etc. 0 K is absolute because it’s not arbitrary (a bit circular I know…). It applies everywhere. Near the Sun or in the outer planets, water freezing is not too useful ---
**Author:** ![Ruken](https://avatars.discourse-cdn.com/v4/letter/r/f475e1/32.png) [@Ruken](https://boards.straightdope.com/u/Ruken)\ **Post date:** [August 4, 2020, 2:48pm UTC](https://boards.straightdope.com/t/apart-from-decibels-are-there-any-other-metric-units-that-are-only-ever-used-with-a-single-prefix/855604/80 "2020-08-04T14:48:05Z")
> [@Ruken](#): > > Re: mmHg, obviously you can measure that with a simple manometer made from a U-tube and a ruler. But our Schlenk lines were pulling 40 millitorr. Before we bought digital ones we had some tilty thing with different diameter tubes for more precise, low-pressure measurements. **I cannot remember the name.** Pardon the bump, but I remembered: > **[McLeod gauge](https://en.m.wikipedia.org/wiki/McLeod_gauge)** > > A McLeod gauge is a scientific instrument used to measure very low pressures, down to 10−6 Torr (0.133 mPa). It was invented in 1874 by Herbert McLeod (1841–1923). McLeod gauges were once commonly found attached to equipment that operates under vacuum, such as a lyophilizer. Today, however, these gauges have largely been replaced by electronic vacuum gauges. > The design of a McLeod gauge is somewhat similar to that of a mercury-column manometer. Typically it is filled with mercury. If used incorr... ---
**Author:** ![pulykamell](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pulykamell/32/3166_2.png) [@pulykamell](https://boards.straightdope.com/u/pulykamell)\ **Post date:** [August 4, 2020, 3:24pm UTC](https://boards.straightdope.com/t/apart-from-decibels-are-there-any-other-metric-units-that-are-only-ever-used-with-a-single-prefix/855604/81 "2020-08-04T15:24:38Z")
> [@Quercus](#): > > Really? I was going to nominate Liter for the OP, since I can’t recall ever seeing liter with any prefix other than milli- (except perhaps in a general way “in the microliter range”). In Hungary, at least, both centiliters and deciliters are commonly used. (Shots at bars are usually given in 2 and 4 centi, and wines quantities are usually given by the deciliter – 2 being typical.) I failed to notice whether this was a particularly Hungarian quirk or not. Picking an arbitrary German bar menu at random (one in Freiburg), I see they list their shots in cLs, as well, but the wine as a decimal part of a liter. [Previous page](https://boards.straightdope.com/t/apart-from-decibels-are-there-any-other-metric-units-that-are-only-ever-used-with-a-single-prefix/855604.md?page=3) [Next page](https://boards.straightdope.com/t/apart-from-decibels-are-there-any-other-metric-units-that-are-only-ever-used-with-a-single-prefix/855604.md?page=5)