# Use of non metric units in the US for scientific purposes **URL:** \ **Category:** Factual Questions\ **Created:** [April 23, 2012, 4:12pm UTC](https://boards.straightdope.com/t/use-of-non-metric-units-in-the-us-for-scientific-purposes/619700 "2012-04-23T16:12:42Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![installLSC](https://avatars.discourse-cdn.com/v4/letter/i/54ee81/32.png) [@installLSC](https://boards.straightdope.com/u/installLSC)\ **Post date:** [April 23, 2012, 7:14pm UTC](https://boards.straightdope.com/t/use-of-non-metric-units-in-the-us-for-scientific-purposes/619700/21 "2012-04-23T19:14:26Z")
I work in a toxicology lab, and _everything_ uses SI–chemicals, glassware, instruments, etc. The only thing I can think of that isn’t primarily in SI is paper for obvious reasons. ---
**Author:** ![Sunspace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sunspace/32/1250_2.png) [@Sunspace](https://boards.straightdope.com/u/Sunspace)\ **Post date:** [April 23, 2012, 8:13pm UTC](https://boards.straightdope.com/t/use-of-non-metric-units-in-the-us-for-scientific-purposes/619700/22 "2012-04-23T20:13:44Z")
And don’t forget that the [US Customary System of Measurements](http://en.wikipedia.org/wiki/United_States_customary_units) is _not_ the [Imperial System of Measurements](http://en.wikipedia.org/wiki/Imperial_units) used by the British Empire after the early 19th century, and _neither_ is the old “English” system that the Imperial system superseded. [A comparison between the US and Imperial systems.](http://en.wikipedia.org/wiki/Comparison_of_the_imperial_and_US_customary_measurement_systems) As a Canadian, I have to deal with ALL of these, except possibly the old English measurements. And it pisses me off. Canada botched its conversion to SI measure by never finishing it, and many fields including publishing, residential house design, and cooking still tend to use Imperial measure. Then there are the differences between US and Imperial measure: when a Canadian ad mentions a car’s fuel usage in “miles per gallon”, is that “miles per US gallon” or “miles per Imperial gallon”? Especially since we buy fuel in litres and measure fuel usage in litres per 100 kilometres? IMHO half this stuff is either comparisons to US models, or sops to the older generations who still stubbornly cling to the old measures. When I was investigating house drawings, I was dragged kicking and screaming backwards from the SI world. I would do my heat and volume calculations in joules and kelvins and millimetres, and convert to BTU/hour and degrees Fahrenheit and cubic feet at the end… especially since our regulations are in SI but our small-scalle typical-handyman construction still tends to take place in feet and inches. Not that I was ever far from it; Canada may be the only country outside the US that still dimensions all its paper in inches as well. So even in ly old job, we usually designed our manuals and publications in inches, often to fit US “letter-size” paper: 8.5 inches x 11 inches. ---
**Author:** ![superfahd](https://avatars.discourse-cdn.com/v4/letter/s/22d042/32.png) [@superfahd](https://boards.straightdope.com/u/superfahd)\ **Post date:** [April 23, 2012, 8:47pm UTC](https://boards.straightdope.com/t/use-of-non-metric-units-in-the-us-for-scientific-purposes/619700/23 "2012-04-23T20:47:18Z")
> [@](#): > > I was dragged kicking and screaming backwards from the SI world I know that feel bro! ---
**Author:** ![minor7flat5](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/minor7flat5/32/258_2.png) [@minor7flat5](https://boards.straightdope.com/u/minor7flat5)\ **Post date:** [April 23, 2012, 9:13pm UTC](https://boards.straightdope.com/t/use-of-non-metric-units-in-the-us-for-scientific-purposes/619700/24 "2012-04-23T21:13:26Z")
> [@Chronos](#): > > But then there are some folks who use pounds for mass _and_ for force, and still use feet and seconds, which means they need to cram an extra factor of something that resembles g all over the place into equations where it has no business being. That would be my shipmates and I studying in Navy Nuclear Power School ages ago. We did everything in English units, including the thermodynamics, chemistry, materials science, reactor theory/nuclear physics. I suppose some of our work was in SI units, but the vast majority was in BTUs, Horsepower, and even lb-m and lb-f. I remember peppering our equations with the “proportionality constant” which was the cheater constant that allowed us to work in lb-f and lb-m at the same time. I recall that all of the charts and graphs were in English units (e.g. steam tables), so maybe that had something to do with it. I wonder if they have gone metric in recent years. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [April 23, 2012, 9:34pm UTC](https://boards.straightdope.com/t/use-of-non-metric-units-in-the-us-for-scientific-purposes/619700/25 "2012-04-23T21:34:53Z")
I work in electromagnetics, and I’ve never used them with English units. When I was first taking physics as an undergrad, we used cgs (centimeter,gram,second), and called it Gaussian units (but I’ve since learned there are more than one set called “Gaussian”). When I began taking electromagnetics in electrical engineering, we used mks (meter,kilogram,second), and different Maxwell’s equations (the fundamental equations of electromagnetics). When I took graduate-level physics, the units were mks, but the equations were more like the ones we used in cgs. Somewhere in there, we used both exp(+j omega t) and exp(-j omega t) time conventions (i.e. whether lossy material will have a positive or negative imaginary part). If you’re counting, that’s three sets of equations/units spread over two time conventions, and none of them were in English units. At work, we use the electrical engineering equations and mks units, which maybe are the SI units, I’m not really sure. I always use meters in any codes I write or work with, immediately converting any inputs in other units. When I have to interface with manufacturing, they usually work in inches or maybe feet, so I know those conversion factors. I still run into both time conventions, and frankly, that’s more confusing than converting between inches and meters. ---
**Author:** ![Nunavut\_Boy](https://avatars.discourse-cdn.com/v4/letter/n/e95f7d/32.png) [@Nunavut\_Boy](https://boards.straightdope.com/u/Nunavut_Boy)\ **Post date:** [April 23, 2012, 9:52pm UTC](https://boards.straightdope.com/t/use-of-non-metric-units-in-the-us-for-scientific-purposes/619700/26 "2012-04-23T21:52:18Z")
> [@installLSC](#): > > I work in a toxicology lab, and _everything_ uses SI–chemicals, glassware, instruments, etc. The only thing I can think of that isn’t primarily in SI is paper for obvious reasons. It may be SI, but for some reason American clinical labs insist on using SI-but-different-from-everyone-else’s-units. For example, US measures glucose (among others) in mg/dl. Everyone else uses mmol/L. Dear god, why? If you’re going SI, why not go with the same units that the rest of the world has agreed on? ---
**Author:** ![Lazlo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lazlo/32/9678_2.png) [@Lazlo](https://boards.straightdope.com/u/Lazlo)\ **Post date:** [April 24, 2012, 1:24am UTC](https://boards.straightdope.com/t/use-of-non-metric-units-in-the-us-for-scientific-purposes/619700/27 "2012-04-24T01:24:28Z")
> [@akennett](#): > > I was a mechanical engineering major in the '90s. We used both slugs and lbm. Same, but I used lbm last month at work. Gotta love good ol’ Crane TP-410. ---
**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:** [April 24, 2012, 1:32am UTC](https://boards.straightdope.com/t/use-of-non-metric-units-in-the-us-for-scientific-purposes/619700/28 "2012-04-24T01:32:41Z")
> [@superfahd](#): > > Ok ok first post. dont mess it up! > > Heres something thats been bothering me for ages. Not being a US native, I’ve done my studies uptil my BS outside the US. I’m a software engineer and have always been keen on scientific topics and courses. One of the most fascinating things for me was the use of the SI (metric) system of units which allows consistent and comparable formulas and calculations not matter what the domain of study is. > > After coming here and realizing that there is a part of the world that doesn’t use the SI system, I was stunned! I simply cant comprehend how the math would work. Do the formulas remain the same or do you have to put in some conversion to account for the wildly inconsistent units of measurement. as a minor example, consider the formula for energy change in a uniform object due to change in temperature (ignoring all other factors) > > E = mc(Δϴ) > > where E = energy change measure in Joules (J) > m = mass measured in kg > c = specific heat capacity measured in Joules per kilogram Kelvin (J/Kg K) > Δϴ = temperature change measured in Kelvin or Centigrade (difference is equivalent in both units) > > Notice that all units are related and the resulting formula is clean and simple and there is no need for conversion of any sort (or even a need to come up with a unit of measurement for the result). Even Joule is just shorthand for (kg.m^2)/s^2 or other equivalent metric units. > > Maybe I’m overthinking this but my brain just BSODs when I even try to think how you would calculate this using pounds for mass, Fahrenheit for tempurature and god knows what for energy or specific heat capacity. Help me out here fellas! I’m going crazy! I work in the (American) auto industry. We work pretty much exclusively in SI units. Well, aside from horsepower and torque; dimensionally its all in SI. Fasteners are all specified with SI dimensions,etc. We might conversationally talk about 6.5" speakers, but we’re really dealing with 165mm speakers. ---
**Author:** ![Diceman](https://avatars.discourse-cdn.com/v4/letter/d/22d042/32.png) [@Diceman](https://boards.straightdope.com/u/Diceman)\ **Post date:** [April 24, 2012, 1:35am UTC](https://boards.straightdope.com/t/use-of-non-metric-units-in-the-us-for-scientific-purposes/619700/29 "2012-04-24T01:35:16Z")
The US automobile industry uses SI for all its design work. Every part on the car has its dimensions spelled out in millimeters – even big parts, where centimeters or even meters might seem more logical. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [April 24, 2012, 1:52am UTC](https://boards.straightdope.com/t/use-of-non-metric-units-in-the-us-for-scientific-purposes/619700/30 "2012-04-24T01:52:05Z")
> [@Sunspace](#): > > Not that I was ever far from it; Canada may be the only country outside the US that still dimensions all its paper in inches as well. So even in ly old job, we usually designed our manuals and publications in inches, often to fit US “letter-size” paper: 8.5 inches x 11 inches. I’m not sure this complaint makes sense. What does it mean to dimension in a unit? If you’re talking about round numbers, then US letter size qualifies, being 11x8.5". But A4 paper does not, being approximately 297.301 x 210.224 mm. Well, they do actually round it down to 297x210, but even so these aren’t nice-looking numbers, given that they derive from multiples of sqrt(2). The only thing even semi-metric about the A-series paper is the area, which for A4 is 1/16 m^2. Which itself looks quaintly Imperial, what with the power-of-2 fraction instead of a power of 10. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [April 24, 2012, 1:55am UTC](https://boards.straightdope.com/t/use-of-non-metric-units-in-the-us-for-scientific-purposes/619700/31 "2012-04-24T01:55:08Z")
> [@Diceman](#): > > The US automobile industry uses SI for all its design work. Every part on the car has its dimensions spelled out in millimeters – even big parts, where centimeters or even meters might seem more logical. My understanding is that the metric system is used in architecture in the same way: millimeters for everything, and unlabeled (except in the legend). Seems like it has lots of advantages, though there’s nothing really specific to the metric system there (you could do the same with inches). ---
**Author:** ![Civil\_Guy](https://avatars.discourse-cdn.com/v4/letter/c/d78d45/32.png) [@Civil\_Guy](https://boards.straightdope.com/u/Civil_Guy)\ **Post date:** [April 24, 2012, 2:05am UTC](https://boards.straightdope.com/t/use-of-non-metric-units-in-the-us-for-scientific-purposes/619700/32 "2012-04-24T02:05:51Z")
Civil engineer. Hey, give us time. Of course, for the rest of time, we’d be forced to figure out how wide the sidewalks will be if we widen the road from 10 to 12 m, given a 60 foot right-of-way. ---
**Author:** ![GameHat](https://avatars.discourse-cdn.com/v4/letter/g/ed655f/32.png) [@GameHat](https://boards.straightdope.com/u/GameHat)\ **Post date:** [April 24, 2012, 2:09am UTC](https://boards.straightdope.com/t/use-of-non-metric-units-in-the-us-for-scientific-purposes/619700/33 "2012-04-24T02:09:39Z")
US doper here, and an engineer (chemical): I graduated college in 2004. All the way through college, the science professors made us use SI (it is a better system, and internationally recognized.) The engineering professors all made us use English units ("yeah, we know SI is better, but industry in the US still uses English units, and it’s not great, but that’s the way it is.) So I got through a chemical engineering degree using (about half the time) grams and joules, the other half using lbs (mass) and BTU. And yep, the formula work the same either way, except there will be a “conversion” constant usually on the English unit formulas. Having been in the chemical industry for nearly 8 years now, yeah. Our manufacturing departments use pounds. Our QC/Analytical/R&D departments use grams and kilograms. Our smaller “shop” customers usually still use pounds. But we sell into Canada as well, and they mostly use kg. Even the smaller shops. So I jump between units every day. I wish we’d all use SI, because it is more intuitive, but institutional inertia is strong. ---
**Author:** ![Sunspace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sunspace/32/1250_2.png) [@Sunspace](https://boards.straightdope.com/u/Sunspace)\ **Post date:** [April 24, 2012, 3:18am UTC](https://boards.straightdope.com/t/use-of-non-metric-units-in-the-us-for-scientific-purposes/619700/34 "2012-04-24T03:18:59Z")
> [@Dr.Strangelove](#): > > My understanding is that the metric system is used in architecture in the same way: millimeters for everything, and unlabeled (except in the legend). Seems like it has lots of advantages, though there’s nothing really specific to the metric system there (you could do the same with inches). When I was in architecture school, they told us that buildings would be dimensioned on a 100-mm ‘module’: that a basic grid of locations at multiples of 100 millimetres would be defined, and things would be referenced to it. Plywood would be 1200 x 2400 mm, studs would be on 400- or 600-mm centres, etc. But. That was thirty years ago. Small-scale residential construction continues in feet and inches. Plywood remains 4 feet x 8 feet (1219 mm x 2438 mm). Studs remain on 16-inch or 24-inch (406 mm or 610 mm) centres. I’ve seen plans for larger constructions dimensioned in metric; for instance, this [railway underpass (Figure 12 on the fourth page of the linked PDF)](http://www.gotransit.com/gts/en/docs/finalEPR/AppendixI_8-15.pdf) has clearances and elevations dimensioned in millimetres, and appears to use metric throughout, with a few Imperial measurements added for reference. (For railways which use miles and miles per hour internally for their own operations…) ---
**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\ **Post date:** [April 24, 2012, 3:30am UTC](https://boards.straightdope.com/t/use-of-non-metric-units-in-the-us-for-scientific-purposes/619700/35 "2012-04-24T03:30:26Z")
In reality the advantages of SI are over rated for most purposes. When I need to know the distance from here to Mars in millimeters, then just being able to shift decimal places will be really handy, but for the most part English units are perfectly suited for the dimensions they are intended. Calculators make converting units trivial and I never have had to convert units on the fly. The one exception is an oven I have at work that works in Fahrenheit, and that drives me batty. ---
**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:** [April 24, 2012, 3:49am UTC](https://boards.straightdope.com/t/use-of-non-metric-units-in-the-us-for-scientific-purposes/619700/36 "2012-04-24T03:49:01Z")
The units being related by powers of 10 is handy, but you’re right that it’s ultimately not that big a deal. What _is_ a big deal, though, is that everything uses the same units. The unit of force is equal to the unit of mass times the unit of length divided by the square of the unit of time. The unit of energy is equal to the unit of force times the unit of distance. The unit of rotational speed is one over the unit of time. All of these are things that do show up regularly in real-world calculations. Here’s a pop quiz: Suppose I have a fish tank that’s 2 feet long by 1 foot wide by 1 1/2 feet high. How many gallons does will it hold? Explain how you got your answer. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [April 24, 2012, 4:24am UTC](https://boards.straightdope.com/t/use-of-non-metric-units-in-the-us-for-scientific-purposes/619700/37 "2012-04-24T04:24:55Z")
> [@Chronos](#): > > Here’s a pop quiz: Suppose I have a fish tank that’s 2 feet long by 1 foot wide by 1 1/2 feet high. How many gallons does will it hold? Explain how you got your answer. May I assume the tank is a rectangular prism? Inside or outside dimensions? If outside, how thick is the glass? How far below the top edge is the water level? How much gravel is there? How big is the tank heater? Rocks? Also, what country do you live in? I joke, but the point is that a simple multiply by 7.48 (assuming US) is an infinitesimal fraction of the entire calculation. The hard parts are the same in SI or Imperial. ---
**Author:** ![thelabdude](https://avatars.discourse-cdn.com/v4/letter/t/dc4da7/32.png) [@thelabdude](https://boards.straightdope.com/u/thelabdude)\ **Post date:** [April 25, 2012, 11:44am UTC](https://boards.straightdope.com/t/use-of-non-metric-units-in-the-us-for-scientific-purposes/619700/38 "2012-04-25T11:44:27Z")
> [@MikeS](#): > > but there’s no particular advantage of a system of units based on the meter and the kilogram versus one based on the foot and the pound-mass. This is true. When I took a job at the Ashland Chemical research headquarters in the70’s, I was appalled to find their resin and plastic group working in pounds and Fahrenheit. I quickly adjusted. I see little utility in water being spg 1.0 when usually you are needing to pounds per gallon or specific gravity. ---
**Author:** ![BigT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bigt/32/12044_2.png) [@BigT](https://boards.straightdope.com/u/BigT)\ **Post date:** [April 25, 2012, 11:49am UTC](https://boards.straightdope.com/t/use-of-non-metric-units-in-the-us-for-scientific-purposes/619700/39 "2012-04-25T11:49:20Z")
> [@superfahd](#): > > [http://en.wikipedia.org/wiki/Pound\_%28mass%29](http://en.wikipedia.org/wiki/Pound_%28mass%29) > > [http://en.wikipedia.org/wiki/Pound\_(force)](http://en.wikipedia.org/wiki/Pound_(force)) > > ok now I’m really confused! It’s no different than the common use of kilograms for weight. ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [April 25, 2012, 11:50am UTC](https://boards.straightdope.com/t/use-of-non-metric-units-in-the-us-for-scientific-purposes/619700/40 "2012-04-25T11:50:53Z")
American biologist here. All SI, all the time. [Previous page](https://boards.straightdope.com/t/use-of-non-metric-units-in-the-us-for-scientific-purposes/619700.md?page=1) [Next page](https://boards.straightdope.com/t/use-of-non-metric-units-in-the-us-for-scientific-purposes/619700.md?page=3)