# 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:** 4
**Author:** ![md2000](https://avatars.discourse-cdn.com/v4/letter/m/73ab20/32.png) [@md2000](https://boards.straightdope.com/u/md2000)\ **Post date:** [May 31, 2013, 4:54pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/61 "2013-05-31T16:54:52Z")
> [@Kenm](#): > > :rolleyes: > > Of course, some things, like 4x8 plywood, 2x4 lumber, etc. don’t change because it’s impossible to change the construction market. . . . Not impossible. 2X4s hadn’t been 2X4s long before metrication. [/QUOTE] Not sure why the roll-eyes. The USA was on the same track as Canada, until the wrath of voters persuaded the government to back off. The government in Canada had 5 years before the next election (not 2) and the courts generally did not interfere as much as they did in the USA, and backbenchers were more intimidated by the party brass (party whip) than by voters… Just the opposite of Congress. (Trudeau himself famously said “backbenchers are nobodies 100 yards 😃 from parliament hill”) So Canada went metric even though it meant trampling peoples’ rights and ignoring a lot of popular will. the whole “big brother tells you you cannot say ‘pounds’ or ‘gallons’ in your store” played out in full. In retrospect, speaking as a physics grad, and simply on a logical basis, the metric system is simpler; it had to be done, and the “short sharp shock” was probably simpler in the long run. But it did trample on people’s rights and it was somewhat disruptive. This sort of change is. I suspect you’ll see the other alternative, gradual change, in the USA. The technolgoy is also simpler today - change units on a scale or gas pump at the push of a button, instead of buying new scales. For example, a simple commerce rule - all new scales bought after X need to be capable of metric. As of Y, all receipts show metric also. You’re already on the way with metric 2L bottles, etc. It will probably be 20 to 50 years before everyone changes even if the government decided to do it. Paper will stay 8.5x11 not A4, N.American sports will still use yards, marathons will stay a nice even 26.4 miles, and so on… In specialized fields, like construction, standard sizes will continue to be historical. Yes, plumbing for example still uses pipes in inch measurements. Lumber nominal sizes, which don’t match finished sizes, are still used. International aviation still uses feet because it’s too disruptive and potentially dangerous to change. ---
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [May 31, 2013, 4:57pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/62 "2013-05-31T16:57:29Z")
> [@md2000](#): > > paper will stay 8.5x11 not a4, n.american sports will still use yards, **marathons will stay a nice even 26.4 miles** , and so on… 26.219(42.195k) 😉 ---
**Author:** ![Pitchmeister](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pitchmeister/32/3459_2.png) [@Pitchmeister](https://boards.straightdope.com/u/Pitchmeister)\ **Post date:** [May 31, 2013, 5:01pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/63 "2013-05-31T17:01:46Z")
> [@Anonymous User](#): > > What makes more sense or at least seems more intuitive (rhetorical question)? 0°C and 100°C being the freezing and boiling points or 32°F and 212°F? It has been said before, but I believe it bears repeating: there’s nothing specifically metric about Celsius. I would keep this point seperate in your discussion, because it weakens the point that you do have. It’s true, metric units of weight and volume make much more sense than their imperial counter parts, but temperature has nothing to do with this. Celsius is just as arbitrary as Fahrenheit, and there’s no switching between different units in temperatures. ---
**Author:** ![MilTan](https://avatars.discourse-cdn.com/v4/letter/m/71e660/32.png) [@MilTan](https://boards.straightdope.com/u/MilTan)\ **Post date:** [May 31, 2013, 5:12pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/64 "2013-05-31T17:12:24Z")
> [@Kenm](#): > > Americans Against Metric, how many pennies in a dollar? How many nickels? How many dimes? How many quarters? How many 10-dollar bills make 100? How many 100s make 1,000? > > Many of you may remember the U.K.'s pre-decimal, base-12 currency. Who in the U.S. didn’t think that was crazy? > > If metric is so awful, why doesn’t the U.S. use base-12 money? Because it would be as crazy as having to remember 5,280 feet make a mile and two pints make a quart and four quarts make a gallon. Not a great example. People have to convert between different monetary units all the time; most people probably do it multiple times a day. In contrast, most people do not have to regularly convert between feet and miles, or square feet and acres, or cubic yards and bushels, or whatever. Even situations like **Chronos** ’s many examples probably come up once a month at most for many people. In fact, I’d guess that if the base-12 currency system had persisted to the present, there would be less incentive to change it: there is far less need to do unit conversions with credit/debit cards. And on a different note, as compelling as it might be to switch to metric for weights and measures, the argument for switching to Celsius from Fahrenheit for general use (as opposed to scientific use) is pretty weak. There’s no issue of unit conversion and both scales are essentially arbitrary. Edit: **Pitchmeister**!!! ---
**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:** [May 31, 2013, 5:16pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/65 "2013-05-31T17:16:38Z")
> [@](#): > > Quoth **DCnDC** : > > 1. um, the exact same amount? > > I know these offhand. Granted, knowledge of acres and cubic inches in gallons is probably not typical, but I’m pretty sure most people know there are 16 tbsp in a cup, which is the one that most likely for most people to encounter. Nope, not the same amount. Note that the recipe came from Ireland, not the US, and quarts, teaspoons, and tablespoons all vary from one side of the Pond to the other. Or maybe whoever wrote down the recipe helpfully converted the units already, since so many of their customers are Americans. Or maybe that person _tried_ to, but knew the quarts were different but didn’t know the tablespoons were different. I don’t know; I still haven’t gotten that recipe to work. The units _aren’t_ standardized, and so they fail in their purpose as units. And you would _hope_ that people would know there are 16 tablespoons in a cup, but I’ve actually had people ask me “How many cups are there in an ounce?”. People really, genuinely don’t understand the American system. Plus, even if you do happen to know that there are 231 cubic inches in a gallon and 4840 square yards in an acre, you still need a calculator. ---
**Author:** ![cochrane](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cochrane/32/10441_2.png) [@cochrane](https://boards.straightdope.com/u/cochrane)\ **Post date:** [May 31, 2013, 5:31pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/66 "2013-05-31T17:31:38Z")
> [@drewtwo99](#): > > I remember trying to explain this to my grandpa and he just couldn’t get it. > > I was telling him, "In the american system, it’s difficult to convert between smaller and larger units. For example, off the top of your head, how many feet are in 3.5 miles? Off the top of my head, I figured there were roughly about 18,000 feet in 3.5 miles. Using my calculator, I multiplied 5280 (the number of feet per mile) by 3.5 and came up with 18,480. Not too bad. It’s easy if you’re accustomed to the conversion factors from a fairly young age. ---
**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:** [May 31, 2013, 5:35pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/67 "2013-05-31T17:35:32Z")
> [@Chronos](#): > > Nope, not the same amount. Note that the recipe came from Ireland, not the US, and quarts, teaspoons, and tablespoons all vary from one side of the Pond to the other. Or maybe whoever wrote down the recipe helpfully converted the units already, since so many of their customers are Americans. Or maybe that person _tried_ to, but knew the quarts were different but didn’t know the tablespoons were different. I don’t know; I still haven’t gotten that recipe to work. The units _aren’t_ standardized, and so they fail in their purpose as units. The units ARE standardized. Just because they use the same terminology does not make them the same system. The fact that imperial units and US units share the same terminology is not a failure of the system, it’s a failure of the language. ---
**Author:** ![ricksummon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ricksummon/32/3333_2.png) [@ricksummon](https://boards.straightdope.com/u/ricksummon)\ **Post date:** [May 31, 2013, 5:52pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/68 "2013-05-31T17:52:11Z")
> [@Chronos](#): > > And you would _hope_ that people would know there are 16 tablespoons in a cup, but I’ve actually had people ask me “How many cups are there in an ounce?”. 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: ---
**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:** [May 31, 2013, 5:56pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/69 "2013-05-31T17:56:16Z")
> [@Thudlow\_Boink](#): > > .. and yield convenient numbers … ideally relatively small whole multiples of the unit itself. That’s why we don’t give the outdoor temperature in Kelvin… I’ve found the digital Celsius control on air conditioners annoying. 25°might be too cold and 26° too hot. Better, I think, were the degree about 45% smaller. 😃 ---
**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:** [May 31, 2013, 5:58pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/70 "2013-05-31T17:58:28Z")
> [@Chronos](#): > > Plus, even if you do happen to know that there are 231 cubic inches in a gallon and 4840 square yards in an acre, you still need a calculator. In most cases, when a person actually needs to know those things, they will be using a calculator anyway. ---
**Author:** ![Kevbo](https://avatars.discourse-cdn.com/v4/letter/k/e47774/32.png) [@Kevbo](https://boards.straightdope.com/u/Kevbo)\ **Post date:** [May 31, 2013, 6:07pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/71 "2013-05-31T18:07:11Z")
Mostly, metric units are sensible and easy to use. There are some cases where it is just silly to use them though: Bicycles: Bicycle standards were long established in inches when metrication took place, so now we have 25.4 mm handle-bars, 28.58mm steerers, 31.75mm headsets, and M14.29 x 1.27 pedal threads, but also lots of actual metric fasteners. This is of course not any easier to keep straight than 1" handle bars, 1-1/8 steerers, 1-1/4" headsets, and 9/16 x 20 pedal threads, and sometimes things don’t fit as well as they’d aught due to rounding error adding to tolerance creep. Seatposts seem especially prone to this…the target size for a given frame could be exact metric or the imperial dimension it was converted (and rounded) from. Threads and gear teeth. Choice of modulus measurement for metric was just stupid. It forces you to use more and more decimal places as you require finer threads. Because of a natural desire to avoid decimals, metric fasteners are often more coarsely threaded than ideal. Cutting metric threads on a lathe (yes, even a metric lathe) is a pain in the ass, as the gear train can’t be reengaged and pick up a partially cut thread the spindle has to be reversed for each pass. There are only a couple of commonly used imperial thread pitches that are not whole numbers and only slightly more that are not even numbers. Metric gear modulus is hard to determine. It is easy to measure an imperial gear at 2" diameter and count the 32 teeth, and know that you are dealing with 16DP gears. Using such gears, the shaft spacing will always need to be in increments of 1/16" inch. Metric uses a modulus system, so to find the pitch, pi gets involved, and the shaft spacing is always screwy and always rounded off, because pi was always used to calculate it. It is a little easier if/when you want to mesh a worm to a gear, (worm drive) as the thread pitch for the worm will come out even in the metric version and some oddball pitch in the imperial. They could have used threads/cm or a metric version of diametrical gear pitch, but they didn’t and what they did use sucks. ---
**Author:** ![UncleRojelio](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/unclerojelio/32/3160_2.png) [@UncleRojelio](https://boards.straightdope.com/u/UncleRojelio)\ **Post date:** [May 31, 2013, 6:10pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/72 "2013-05-31T18:10:35Z")
Now that you can type “convert 27 mph to furlongs per fortnight” into Google and get an instantaneous answer, what does it matter what units folks choose to measure things in? ---
**Author:** ![Flyer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/flyer/32/7298_2.png) [@Flyer](https://boards.straightdope.com/u/Flyer)\ **Post date:** [May 31, 2013, 6:12pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/73 "2013-05-31T18:12:26Z")
> [@Anonymous User](#): > > Metric is much more intuitive [snip]. Wrong–a thousand times wrong. The traditional system of measurement was developed precisely BECAUSE it was intuitive. A foot is fairly close to the length of the average adult foot. A yard is about how far apart most people tend to stretch their arms when they want to measure something. It’s also close to the length of the average stride. Half a yard is the distance from fingertip to elbow. An acre is the amount of land that a team of oxen could plow in a day. Furthermore, metric is absurd in many ways. If I want to tell somebody how tall I am in metric, I have only two ways that are even slightly reasonable–either use a percentage of meters, or else use hundreds of centimeters. Both are absurd. In contrast, the inch works perfectly well for most short measurements, and the foot works very well indeed for human-sized measurements. In short, the traditional system is far more flexible, and thus is far more sensible. ---
**Author:** ![md2000](https://avatars.discourse-cdn.com/v4/letter/m/73ab20/32.png) [@md2000](https://boards.straightdope.com/u/md2000)\ **Post date:** [May 31, 2013, 6:16pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/74 "2013-05-31T18:16:00Z")
> [@runner pat](#): > > 26.219(42.195k) 😉 Oh, so what was my error in feet? ---
**Author:** ![tracer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tracer/32/20578_2.png) [@tracer](https://boards.straightdope.com/u/tracer)\ **Post date:** [May 31, 2013, 6:19pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/75 "2013-05-31T18:19:40Z")
A couple of **videos** I’ve made about the subject: [Ambiguity in U.S. customary units](http://www.youtube.com/watch?v=XI9w8g4UT2I) [Decimal subdivisions in U.S. customary units](http://www.youtube.com/watch?v=fdSRTJu6mSM), for those of you who believe U.S. customary units are more “natural” because they’re divided into 1/12 or 1/16 instead of 1/10. ---
**Author:** ![Kenm](https://avatars.discourse-cdn.com/v4/letter/k/bc79bd/32.png) [@Kenm](https://boards.straightdope.com/u/Kenm)\ **Post date:** [May 31, 2013, 6:20pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/76 "2013-05-31T18:20:13Z")
> [@Flyer](#): > > An acre is the amount of land that a team of oxen could plow in a day. Eminently sensible. ---
**Author:** ![Yllaria](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yllaria/32/3452_2.png) [@Yllaria](https://boards.straightdope.com/u/Yllaria)\ **Post date:** [May 31, 2013, 6:22pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/77 "2013-05-31T18:22:04Z")
> [@For You](#): > > Yes, but the question was a pound: one pound troy is twelve troy ounces. :smack: Thanks. ---
**Author:** ![marshmallow](https://avatars.discourse-cdn.com/v4/letter/m/df705f/32.png) [@marshmallow](https://boards.straightdope.com/u/marshmallow)\ **Post date:** [May 31, 2013, 6:26pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/78 "2013-05-31T18:26:33Z")
[Mandatory image.](http://2.bp.blogspot.com/-A-DI_BEnI6o/TzDmNAz-jTI/AAAAAAAACp8/1NoynS8RoYU/s1600/US+measures.jpg) ---
**Author:** ![Kimballkid](https://avatars.discourse-cdn.com/v4/letter/k/b5a626/32.png) [@Kimballkid](https://boards.straightdope.com/u/Kimballkid)\ **Post date:** [May 31, 2013, 6:27pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/79 "2013-05-31T18:27:18Z")
> [@Anonymous User](#): > > What is the purpose of the US customary system of measurement? To mess with little know-it-alls that think they are smarter than everyone else. > [@Anonymous User](#): > > more intuitive measurement system? That phrase, I do not think it means what you think it means. I don’t think the metric system is at all intuitive. ---
**Author:** ![tracer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tracer/32/20578_2.png) [@tracer](https://boards.straightdope.com/u/tracer)\ **Post date:** [May 31, 2013, 6:28pm UTC](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784/80 "2013-05-31T18:28:24Z")
> [@Chronos](#): > > And you would _hope_ that people would know there are 16 tablespoons in a cup, but I’ve actually had people ask me “How many cups are there in an ounce?”. If by “ounce” you mean a U.S. fluid ounce, the answer is: 0.125. [Previous page](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784.md?page=3) [Next page](https://boards.straightdope.com/t/what-is-the-purpose-of-the-us-customary-system-of-measurement/659784.md?page=5)