# What is the purpose of the US customary system of measurement? **URL:** \ **Category:** Factual Questions\ **Created:** [May 31, 2013, 1:57pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784 "2013-05-31T13:57:03Z")\ **Posts on this page:** 20\ **Page:** 9
**Author:** ![eschereal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschereal/32/18939_2.png) [@eschereal](https://boards.straightdope.com/u/eschereal)\ **Post date:** [June 1, 2013, 3:06pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/161 "2013-06-01T15:06:23Z")
I could see replacing astronomical distances with prefixed meters. A light-year would be about 9.46 Pm, a parsec about 31 Pm, there would be about 105 ly in an Em, the Milky Way would be about one Zm across. Sure makes the language more compact. ---
**Author:** ![drewtwo99](https://avatars.discourse-cdn.com/v4/letter/d/d07c76/32.png) [@drewtwo99](https://boards.straightdope.com/u/drewtwo99)\ **Post date:** [June 1, 2013, 3:08pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/162 "2013-06-01T15:08:17Z")
> [@AaronX](#): > > Those used to the imperial system - can you convert, say, 2.567 km to miles, feet, inches? How many operations on a calculator does it take you? Grandpa, is that you? ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [June 1, 2013, 3:25pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/163 "2013-06-01T15:25:27Z")
the purpose of keeping the english system is an attempt to keep people sharp in their arithmetic skills and pressure from the slide rule industry. ---
**Author:** ![AaronX](https://avatars.discourse-cdn.com/v4/letter/a/7bcc69/32.png) [@AaronX](https://boards.straightdope.com/u/AaronX)\ **Post date:** [June 1, 2013, 3:32pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/164 "2013-06-01T15:32:55Z")
> [@drewtwo99](#): > > Grandpa, is that you? No, this grandpa is metric. ---
**Author:** ![Kenm](https://avatars.discourse-cdn.com/v4/letter/k/bc79bd/32.png) [@Kenm](https://boards.straightdope.com/u/Kenm)\ **Post date:** [June 1, 2013, 3:35pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/165 "2013-06-01T15:35:28Z")
> [@AaronX](#): > > Those used to the imperial system - can you convert, say, 2.567 km to miles, feet, inches? How many operations on a calculator does it take you? I have a metric-converter hand-held calculator. Punch in the number and hit the From Metric or To Metric button, then the category button, kilometres/miles, square kilometres/square miles, litres/imperial gallons, litres/U.S. gallons and so on. According to the calculator, 2.567 kilometres = 1.59505985 miles. I have [**this calculator**](http://www.amazon.com/gp/product/B000QGPYTA/ref=olp_product_details/192-5757119-1322247?ie=UTF8&me=&seller=). The listed price is ridiculous. I picked mine up for 8 bucks at Staples. ---
**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:** [June 1, 2013, 3:59pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/166 "2013-06-01T15:59:32Z")
> [@ricksummon](#): > > I once saw a game show in which a woman was asked “How many teaspoons are in a tablespoon?” She said “four”, but the correct answer was “three”. _Then_ she said, “But that _can’t_ be! I wrote a _cookbook!_” :smack: Yeah, I cook nearly every single day; I know 3 tsp=1 tbsp; I know conversions from fluid oz. up to gallons, and that Imperial and US are different. But I never can remember it’s 16 tbsp to a gallon. I rarely need to know that, but when I do, I have to look it up. I suspect it’s not a very well-known conversion, as opposed to four quarts in a gallon. ---
**Author:** ![AaronX](https://avatars.discourse-cdn.com/v4/letter/a/7bcc69/32.png) [@AaronX](https://boards.straightdope.com/u/AaronX)\ **Post date:** [June 1, 2013, 4:03pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/167 "2013-06-01T16:03:27Z")
> [@Kenm](#): > > I have a metric-converter hand-held calculator. Punch in the number and hit the From Metric or To Metric button, then the category button, kilometres/miles, square kilometres/square miles, litres/imperial gallons, litres/U.S. gallons and so on. > > According to the calculator, 2.567 kilometres = 1.59505985 miles. > > I have [**this calculator**](http://www.amazon.com/gp/product/B000QGPYTA/ref=olp_product_details/192-5757119-1322247?ie=UTF8&me=&seller=). The listed price is ridiculous. I picked mine up for 8 bucks at Staples. I know, but how many feet is 0.59505985 miles? How many inches is the decimal part of that? ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [June 1, 2013, 4:30pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/168 "2013-06-01T16:30:08Z")
> [@Martin\_Hyde](#): > > You make a point as to why we don’t really need any legislative change, though…You’ve made a good argument for use of SI measurements in a few places, and that sounds like the people who do that kind of work should use that system–and it appears they do. Has nothing to do with anyone’s day to day use of the measurement system though. Large swathes of the population in fact don’t often need to measure things using a measurement system at all. This may seem to be true, but the problem with that is that the units in which technical calculations and measurement are done in have to be converted at some point to units used by the general public, and the potential for error in the additional calculations (both from incorrectly performing the conversion and the previously mentioned floating point or significant figure errors) can be problematic. The failure of the Mars Climate Orbiter due to a units conversion issue is the most dramatic example, but there are others in manufacturing and transportation which are more pertinent to everyday life. That many building codes, regulations, and contracts in the United States still specify units of measurement in SI tends to increase the inertia to not converting even when it makes sense to do so. But you are correct, where it is sensible–such as in industries like automobile manufacturing or pharmaceuticals–the industries have volunarily converted (for the most part) in order to make better use of global supply chains and compliance with regulations. As for the points made by several that US customary units are somehow more “intuitive”, these are merely rationalizations. The average adult foot is not 12 inches (2.54 cm) in length, and the variance of a foot (from about 10 to 16 inches at two standard deviations) is sufficient that measuring by pacing is only slightly more accurate than a skilled measure by eye. The finer graduations offered by the Fahrenheit temperature scale are not physically discernable by the vast majority of people, and the division of the Celsius scale from -10 to 40 (with the freezing and boiling temperatures of water at standard pressure at 0 and 100 °C) are quite aguably more sensible for the natural temperature variations tolerable by human beings. That US Customary units are more familiar is not in question, but switching to SI units for everyday measure is not this tragic and herculean effort for any person with an IQ above 90 who isn’t actively resisting the change, any more than it is impossible for someone to recalibrate their scale of “what things cost” when going from US dollars to Euros or Yen. All measures are artificial and their degree of “intuitiveness” is really based upon having a reasonable scale compared to the quantities being measured and the base of the calculation system (hence why metric units make carrying significant digits and rounding errors easier to manage). Consider that prior to a little over two centuries ago there was almost no standardization in units of measure, and in fact, the standardization of units was done precisely to facilitate industrialization and internatoinal trade. That the vast majority of the world uses metric units for everyday measures argues against US Customary units–or any other native measures–as being inherently better or easier to interpret. Regarding the neper (or decibel), while it can be considered a unit and is “metric” in the base 10 numbering system, it is not a unit of measurement, but rather a ratio of measures or of a measured value such as power or pressure to a normalized base. For instance, decibels in sound are calcualted against a reference value of 20 micropascals above the ambient pressure level such that a microphone captures the local pressure deviation and calculates the sound pressure level (SPL) = log(root mean square of the measured pressure)/log(20 µPa) for a given frequency band. The neper or decibel are not part of the SI system, although when used with an SI system of units are compatible with it and make it easier to handle quantities which scale exponentially to a numerical base. Stranger ---
**Author:** ![Martin\_Hyde](https://avatars.discourse-cdn.com/v4/letter/m/47e85d/32.png) [@Martin\_Hyde](https://boards.straightdope.com/u/Martin_Hyde)\ **Post date:** [June 1, 2013, 4:32pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/169 "2013-06-01T16:32:18Z")
> [@AaronX](#): > > I know, but how many feet is 0.59505985 miles? How many inches is the decimal part of that? How often would you imagine a user of the U.S. customary system would _need_ to know this? Inches and feet are most commonly used to either measure living things, or in construction or similar activity, and things like measuring if your room is wide enough to fit the new couch you’re thinking of buying. By and large we don’t measure miles _at all_, because they are too big, anymore than the average metric user measures _anything_ in kilometers. The only time we might use miles would be on a trip, and I’d never have a need to convert from miles to feet/inches. It gets back to what I’m saying, where it makes sense most Americans that need it already use the metric system. But average people have little if any cause to ever convert from miles to feet and inches–in fact I’ve never done it in the entirety of my life outside of when I was a little kid and had to learn that 1 mile = 5,280 feet. At that length it’s too big a unit to use in daily life. But that’s roughly the same as a kilometer, I imagine a driver can “roughly tell” when they’ve driven a km if they’re used to it, but can they tell when they’ve gone 100m versus 480m? Unlikely, no more than I can easily tell if I’ve gone 200 ft versus 520 ft. [Now I bet most Americans can roughly guesstimate yards, because we know 100 yards is a football field so we can sorta roughly think–okay, the next street I turn at is 2 football fields away–but that’s not a common thing either.] ---
**Author:** ![DCnDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dcndc/32/2842_2.png) [@DCnDC](https://boards.straightdope.com/u/DCnDC)\ **Post date:** [June 1, 2013, 4:33pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/170 "2013-06-01T16:33:19Z")
> [@AaronX](#): > > I know, but how many feet is 0.59505985 miles? How many inches is the decimal part of that? I’ll give you the answer if you can give me a legitimate, practical, everyman reason why I would need to know that. ---
**Author:** ![Martin\_Hyde](https://avatars.discourse-cdn.com/v4/letter/m/47e85d/32.png) [@Martin\_Hyde](https://boards.straightdope.com/u/Martin_Hyde)\ **Post date:** [June 1, 2013, 4:36pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/171 "2013-06-01T16:36:33Z")
> [@Stranger\_On\_A\_Train](#): > > This may seem to be true, but the problem with that is that the units in which technical calculations and measurement are done in have to be converted at some point to units used by the general public, and the potential for error in the additional calculations (both from incorrectly performing the conversion and the previously mentioned floating point or significant figure errors) can be problematic. The failure of the Mars Climate Orbiter due to a units conversion issue is the most dramatic example, but there are others in manufacturing and transportation which are more pertinent to everyday life. That many building codes, regulations, and contracts in the United States still specify units of measurement in SI tends to increase the inertia to not converting even when it makes sense to do so. But you are correct, where it is sensible–such as in industries like automobile manufacturing or pharmaceuticals–the industries have volunarily converted (for the most part) in order to make better use of global supply chains and compliance with regulations. Well I know it’s a fun story but the Mars Climate Orbiter failure is really a pretty poor example when responding to my claim that most people in their day-to-day lives would realize few if any of the benefits of a change. I imagine vanishingly few people on the forums here are involved in the design of NASA vehicles (maybe 1-2 might be, maybe.) But I think there’s probably a bigger reason than just building codes that most of the construction trade still works with customary units–because it doesn’t appear that metric is intrinsically that advantageous in that industry. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [June 1, 2013, 4:39pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/172 "2013-06-01T16:39:10Z")
> [@septimus](#): > > Interesting. I wonder if this is true of all near-Equator countries, or whether your closeness to _two_ oceans is key: when one is warming you the other cools, and vice versa. Just one is sufficient, I think. I live two blocks from the Pacific Ocean. During the warmest time of year the trade winds are blowing, and that helps it feel cooler. It gets a bit hotter in the so-called “interior,” but only to maybe 35 C. No place in Panama is more than about 40 km from the sea. I used to live in Washington DC. Panama has a better climate in both the winter _and_ the summer.😃 ---
**Author:** ![hibernicus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hibernicus/32/2802_2.png) [@hibernicus](https://boards.straightdope.com/u/hibernicus)\ **Post date:** [June 1, 2013, 4:44pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/173 "2013-06-01T16:44:32Z")
> [@pulykamell](#): > > Yeah, I cook nearly every single day; I know 3 tsp=1 tbsp; I know conversions from fluid oz. up to gallons, and that Imperial and US are different. But I never can remember it’s 16 tbsp to a gallon. Did you mean 16 cups? There are 16 x 16 tbsp in a gallon. ---
**Author:** ![septimus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/septimus/32/410_2.png) [@septimus](https://boards.straightdope.com/u/septimus)\ **Post date:** [June 1, 2013, 5:10pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/174 "2013-06-01T17:10:25Z")
All widths _very_ approximate: yoctometer - neutrino zeptometer - top quark (x 10) attometer - up quark femtometer - proton picometer - uranium nucleus (x 100) or helium atom (x 0.05) nanometer - glucose molecule micrometer - largest virus or smallest bacterium millimeter - tiny insect meter - dodo bird kilometer - Vatican City megameter - Italy gigameter - Sun (x 0.6) terameter - Antares petameter - Stingray Nebula exameter - Rosette Nebula zettameter - Milky Way Galaxy yottameter - Virgo supercluster When I hung out with electrical engineers 40 years ago, _pico_ was the smallest prefix in wide use. (picofarad was in such frequent use, it was abbreviated as “puff.”) But I don’t recall hearing _giga_ except half-jokingly. How about now? One can buy a terabyte hard drive for a few dollars at the supermarket. :smack: What else? ---
**Author:** ![Smapti](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/smapti/32/17938_2.png) [@Smapti](https://boards.straightdope.com/u/Smapti)\ **Post date:** [June 1, 2013, 5:44pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/175 "2013-06-01T17:44:21Z")
> [@AaronX](#): > > Those used to the imperial system - can you convert, say, 2.567 km to miles, feet, inches? How many operations on a calculator does it take you? I _could_ do that. Or I could say it’s 1.6 miles and leave it at that, because unless I’m trying to pass a middle-school math test I can’t fathom any reason why 1.6 miles wouldn’t be an acceptable solution. Of course, if you’re trying to be needlessly pedantic, one wonders why you haven’t asked us to compute it in miles, furlongs, chains, rods, yards, feet, and inches. ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [June 1, 2013, 5:49pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/176 "2013-06-01T17:49:34Z")
> [@septimus](#): > > All widths _very_ approximate: > > yoctometer - neutrino > zeptometer - top quark (x 10) > attometer - up quark > femtometer - proton > picometer - uranium nucleus (x 100) or helium atom (x 0.05) > nanometer - glucose molecule > micrometer - largest virus or smallest bacterium > millimeter - tiny insect > meter - dodo bird > kilometer - Vatican City > megameter - Italy > gigameter - Sun (x 0.6) > terameter - Antares > petameter - Stingray Nebula > exameter - Rosette Nebula > zettameter - Milky Way Galaxy > yottameter - Virgo supercluster No, no, no. After zeptometer it goes harpometer, chicometer, grouchometer.😛 ---
**Author:** ![lance\_strongarm](https://avatars.discourse-cdn.com/v4/letter/l/87869e/32.png) [@lance\_strongarm](https://boards.straightdope.com/u/lance_strongarm)\ **Post date:** [June 1, 2013, 5:51pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/177 "2013-06-01T17:51:15Z")
> [@Stranger\_On\_A\_Train](#): > > The failure of the Mars Climate Orbiter due to a units conversion issue is the most dramatic example, Yes, that’s a dramatic example of how our clinging to the old system can cause massive failure. ---
**Author:** ![AdamF](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/adamf/32/6246_2.png) [@AdamF](https://boards.straightdope.com/u/AdamF)\ **Post date:** [June 1, 2013, 5:52pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/178 "2013-06-01T17:52:25Z")
> [@Mdcastle](#): > > As I noted last time, much of the US is surveyed in mile square “sections”, with roads along the section lines and blocks and acres in neat increments. Using metric here would be extremely messy. > [@Spectre\_of\_Pithecanthropus](#): > > And each section being divisible into 640 acres, this is why parcels of farm land often occur in multiples of 40 acres, and also why we hear about the ‘back 40’ or ‘east 80’ in rural contexts. The situation is already quite messy. It is not possible to fit Earth’s surface into rectilinear grid. In fact, only 25 out every 36 sections have 640 acres. The others may be up to 10% larger or smaller. Additional space may have been lost/gained for roads and other easements. Likewise, roads are 1 mile apart only at a specific parallel that was used for the survey. at any other point, the spacing is larger/smaller. It is just like 2x4s - just because we call it one thing, it doesn’t mean that is the exact dimension. ---
**Author:** ![lance\_strongarm](https://avatars.discourse-cdn.com/v4/letter/l/87869e/32.png) [@lance\_strongarm](https://boards.straightdope.com/u/lance_strongarm)\ **Post date:** [June 1, 2013, 5:59pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/179 "2013-06-01T17:59:28Z")
> [@Smapti](#): > > I _could_ do that. > > Or I could say it’s 1.6 miles and leave it at that, because unless I’m trying to pass a middle-school math test I can’t fathom any reason why 1.6 miles wouldn’t be an acceptable solution. > > Of course, if you’re trying to be needlessly pedantic, one wonders why you haven’t asked us to compute it in miles, furlongs, chains, rods, yards, feet, and inches. It’s not 1.6 miles though. You already made a mistake. Since you have to keep track of all these conversion factors, the mistakes add up. It’s actually 1.6 km in a mile, not the other way around. And the question was not how many miles in 1 km, it was how many in 2.567 km. So you have to get out your calculator. Meanwhile, there are exactly 2567 meters in 2.567 km. I didn’t have to remember a conversion factor or do any math other than moving a decimal point. ---
**Author:** ![lance\_strongarm](https://avatars.discourse-cdn.com/v4/letter/l/87869e/32.png) [@lance\_strongarm](https://boards.straightdope.com/u/lance_strongarm)\ **Post date:** [June 1, 2013, 6:02pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/180 "2013-06-01T18:02:26Z")
Suppose I propose a new money system with 135.7 pennies per dollar. A dime is worth 38.3 pennies. A nickel is 14.2 pennies. I think most people would instantly see how completely stupid that system would be and reject it. [Previous page](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784.md?page=8) [Next page](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784.md?page=10)