Why it is hard for US to move to metric system?

Purely political. There were plans in place in the 70s and 80s. A particular political party politicised it as some sort of government overreach/UN/NWO meddling. And once they had the votes they voted to strip any mention of metric in federal usage. States followed shortly.

I learned both metric and imperial measurements in elementary, middle, and high school. From what I understand they only use metric in science classes now.

It didn’t make sense to me at the time. But the. I saw what happened to Core Curriculum, CRT, and US history. And it all makes a lot more sense.

I mean the UK still does roads/cars in MPH rather than KPH. Lots of people will still give their (body)weight/ask for (body)weight in stone and height in feet and inches, although I think that's slowly changing to KG and CM.

It's a strange one though, isn't it? I was watching an exercise/nutrition video on YouTube earlier and the presenter was saying "to work out how much protein a day you need, multiple your bodyweight in lbs by X and that will give you the protein number in grams." It seemed so bizarre to combine the systems.

Edit: Just to add - in the UK we're taught entirely in metric in school, the bits mentioned above are just hangups / how it's done.

Having grown up in a country into adulthood that used metric and then moving to the US there are certain things that are nice about the US system.

In particular a foot is an extremely intuitive unit of measure. It covers a number of use cases better than meters or centimeters.

I also prefer Fahrenheit now that I'm used to it. Fahrenheit has a nicer range for the temperatures we live our lives at, whereas Celsius compresses that range so much.

Unintuitive US units: Miles - I still have a very hard time with how far this is, km was much nicer.

As a European I only get mildly upset when reading US recipes. "1 cup of flour" Just the fact that it's a measure of volume [0] instead of weight is already stupid imo. I pretty much stopped reading recipes where there are no metric units (weight!) provided, preferably in grams.

0, https://en.wikipedia.org/wiki/Cup_(unit)

1. Inertia. It is difficult to switch measurement in people's heads. For example, I grew up in metric environment, but I did not drive car. So for me, local sizes are in meters, but car speed, distances are in miles :-). Home temperature is in Celsius, but grill or oven are in Farenheits. :-)

2. Cost. There is a direct cost (like remarking everything), and indirect -- all the chaos and errors because of mixing up units. To foot the bill is hard sell in Congress.

3. Peer pressure: because of size of economy, US can request whatever it wants from partners. UK had to move to metric when joined EU.

That said, I am very supportive of metric. We are paying price for the imperial units. Every car shop has two set of wrenches. (BTW, it is metal, production -- read climate impact. May be not big, but still impact we could avoid.) All the software must show controls for units. We need to train professionals (like doctors) to live in two worlds. And the list is endless. [Did I mention translation bugs? For example, outside temperature translation is 9/5 Celsius + 32, but difference between outside and inside is 9/5 Celsius. :-( -- real bug I caught in critical industrial control system. ]

I am not sure where does US stands today. For example, I think metrics is teached in school. Most food is dual marked. So, maybe, it is not rejection, but rather slow move?

The US uses metric for some things, so it's partly transitioned.

Feels like something that's only going to go in one direction, even if not quickly in some cases.

The US does use metric system (you can easily go and buy 2 liter bottle of Coke). What you probably mean, why the metric system is not mandated as the only one acceptable for basically everything? Why indeed.

We tried it in the 70's. Signage everywhere (well, almost everywhere) used to have both kilometer and mile distances. Speedometers had both dials. Thermometers had two scales. Etc. etc.

Then... it just never completely took. Then those changes went away.

Part of it was political, surely (Carter spearheaded the metric change; Reagan coming in was super conservative), but I think you underestimate just how hard it is to get 50 halfway-independent states and millions of people to all agree on an entirely new system of measurement (not just of distance, but of volume, temperature etc.) when in millions of people's brains, the number 72 means "comfortable" (in Fahrenheit) and 100 means "hot!" (again, in Fahrenheit... you can't say "temps are in the triple digits!" in Celsius and have it mean anything other than that you're boiling), a tall man is "over 6 feet tall!", the average weight of an adult is 180 pounds, ovens get heated to 375 to bake something usually, shoe sizes (in inches), belt lengths (in inches), heck my baby's perfect bathwater temperature is exactly "100 degrees" (F, measured via infrared thermometer), going "100MPH" is VERY fast, 0 degrees F is VERY cold (-17C), etc. etc.

It's still used in some spaces like science, but in places like tooling it's both... I have 2 sets of EVERY TOOL (well, every tool with a fixed size at least, like sockets and allen-head wrenches), the metric version and the imperial version, it's maddening- basically the worst of all options is to get stuck in the middle, and that's precisely what happened with tooling.

Lastly, the digital tooling to automatically or easily convert is getting more common (a certain Reddit bot comes to mind which automatically converts any Imperial measurements cited in comments to metric), heck a browser plugin could probably do it for you

The imperial system has a great UX and is as precise as metric so there's no real incentive to change. For science metric makes a lot of sense of course and we use it there (mainly!) and we use it for trade, but for day-to-day use among people, why change? It's very intuitive in terms of unit sizes being very much at human scale. Even when doing woodworking/carpentry, the imperial system is really nice being based on 12 in many aspects. The foot/inch system is great for day to day use. The centimeter is too small and the meter too large, for example.

I also think it's nice that different countries do things differently. It gives you identity and makes the world a more diverse and interesting place. I love that the UK has measurements like "stone" when describing a person's weight and that they use miles per hour for driving and kilograms for buying food and drive on the left side of the road.

A difficulty that I find is that metric as commonly used is more awkward for estimating.

For example, I find that metric distance as commonly used doesn't have a good equivalent to feet for working with medium lengths. By "as commonly used" I mean that, while I could theoretically use decameters, in practice average people seem to only use millimeters, centimeters, meters, and kilometers. That makes it difficult for me to estimate medium lengths in metric. For example, it's awkward to describe someone as 1.83 meters or 183 centimeters tall. It is much easier to describe them as 6 feet 2 inches.

To a somewhat lesser degree, the same seems to be true for volume. In practice people only seem to use milliliters and liters. That leaves me with no good equivalent to cups or gallons.

The vast majority of organizations in the US already use the metric system in places where the metric system makes sense. Basically everyone who wants to use it is already using it.

For everything else, what's the point in the government mandating it? There's no political desire for it because society in general doesn't care, and society doesn't care because the costs outweigh the benefits. There's no practical advantage to the average person to learn their height in meters instead of inches and feet, or to have to start shopping for hectograms of food when ounces work just fine.

I'm not sure it's hard, is there evidence? Personally I don't think there's any valuable benefit, certainly not worth all the resulting disruption, and wouldn't advocate for it for that reason.

Not answering the OP but instead sharing what I am having to do to accommodate others while learning a thing or two through that accommodation. Some here may recall the significant NASA failure where imperial and metric were mixed leading to a costly outcome(1) and that is what I want to avoid. While I am not launching rockets I do require extremely accurate calculations for my objectives. As an American, born and raised, the U.S. way is baked into everything that I do; however now that I am engineering a global hardware based solution that sees neither race, nationality, or creed all my engineering calculations are presented in metric in the final “pitch”. As an American I have done all my "internal thinking" using what I know but to reach a broader market for my potential global audience my documentation carries the reader, should they be Imperial based, through the metric conversions for those with the mathematical interest. My past experiences have guided me to spend the time now for this activity as a function of explicit documentation presenting the engineering and this is time very well spent since explicit written calculations with variables and constants clearly labeled leave much 'less' room for error when assumptions are eliminated, regardless of your unit of weights and measure.

(1)https://www.newscientist.com/article/dn17350-nasa-criticised...

As the joke goes, there are two types of countries: Those that use the metric system, and those that have been to the moon.

All joking aside, the metric system is widely used in the US for guns and drugs.

The switch to Metric in the US was made easier by a personal decision of Carl Johansson... (backed up by wikipedia)[1]

  In the early 20th century, the U.S. inch was effectively defined as 25.4000508 mm (with a reference temperature of 68 °F (20 °C)) and the U.K. inch at 25.399977 mm (with a reference temperature of 62 °F (17 °C)). When Johansson started manufacturing gauge blocks in inch sizes in 1912, Johansson's compromise was to manufacture gauge blocks with a nominal size of 25.4mm, with a reference temperature of 20 °C (68 °F), accurate to within a few parts per million of both official definitions. Because Johansson's blocks were so popular, his blocks became the de facto standard for manufacturers internationally, with other manufacturers of gauge blocks following Johansson's definition by producing blocks designed to be equivalent to his.

[1] https://en.wikipedia.org/wiki/Gauge_block

Actually USA is using the metric system.

They just apply their weird conversions on top of the metric system, but fundamentally they use the definitions of the International System of Units.

E.g. Pound is legally exactly 0.45359237 kilograms where kilogram is defined by setting the Planck constant h exactly to 6.62607015×10^−34 J⋅s (J = kg⋅m2⋅s^−2), given the definitions of the metre and the second.

Previously kilogram was a block of metal stored in France. But the copies of kilogram were diverging and there was no way of knowing where the changes were coming from. So now the kilogram is defined with regard to the physical properties of the universe as opposed to specific object.

E.g. a meter is exactly the distance traveled by light in a vacuum in 1/299792458 seconds. Where second is exactly the duration of 9192631770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom.

I grew up in the US. I only learned the metric system. There was never any point at which we used the customary units.

There's a few reasons for this.

First, the 10-based units of the metric system isn't in fact its biggest utility--it's the fact that everyone agrees on the size of the meter, as opposed to the traditional foot, where every country had its own slightly different length of a foot. With those other customary units pretty thoroughly dead, there's little confusion as to the size of a foot.

Second, as a few people have noted, customary units actually tend to be somewhat more convenient to use than a strict metric system. Note that the metric system comes up with 1 liter = (1/10 m)^3 or 1 hectare = (100 m)^2 to try to synthesize useful volume or area units from regular length. In many regards, Fahrenheit is really a more comfortable measure of ambient air temperature than Celsius is. The metric system's fastidiousness in 10-based increments is more useful if you're doing tasks like measuring the area of an irregularly-shaped plot of land, or scientific calculations, but is less useful for more pedestrian tasks like measuring out how much flour you need for the cake you're baking.

Third, it takes a very long time (at least a generation) for people to get used to new units. You see this in the UK, where imperial units are still used for lots of things despite official metrication. Residual use of customary units for things like cookbooks or tool dimensions will take a very, very long time to root out.

Finally, there are lots of things that depend on the precise units that are hard to move. The US actually has two definitions of length, the international foot (which has 1 in = 2.54 cm exactly), and the survey foot (which has 39.37 in = 1m exactly). It's been trying to phase out the survey foot for decades, and that's still in progress because quite literally the coordinate planes that are used in several states for plotting land in the US are based on the survey foot. Even small differences in units there can lead to inaccuracies of several feet in determining the bounds of your plot of land.

we don't want to: 12 is more divisible than 10

US standard may be worse, but the USA is the leader of the free world and is not about give up the choice to use other systems and bases like duodecimal and bow to some arbitrary tyrannical French system imposed by a despot that declares decimal to be the end all be all.

Nit: For those saying the US uses Imperial units. It doesn't.

The US uses something called US Customary Units:

https://en.wikipedia.org/wiki/United_States_customary_units

Both US Customary & Imperial derived from British units but they have always had large differences. There was an effort to reconcile the two but it was an abandoned when Europe decided to adopt the metric system.

Still differences remain:

https://en.wikipedia.org/wiki/Comparison_of_the_imperial_and...

Driving the Alaska Highway there are a bunch of markers for historical things along the road like bridges & lookouts. The majority of the Alaska Highway is actually in Canada, and so all the signs are now in Kilometers and they say things like "Historical marker 1550km (old mile marker 965)".

I was standing at one taking a look and an older couple came over and loudly exclaimed "It's a damn sacrilege to the memory of those young men who built the road they would go and change it like that."

They were adamant changing it to kilometers was unacceptable, because old reasons.

The US is moving toward the metric system, slowly. Federal efforts may have largely stalled during the Reagan admin (though things like requiring metric labeling on products still eventually made it through), but there's nothing stopping individual states from requiring metric in more places, e.g. road signs. As for why no state has bothered to do so yet, it's likely because there's currently a thousand more pressing issues to expend political capital on first, many of which are existential crises in a way that metrication is not.

Adam Ragusea has an excellent video on this topic: https://www.youtube.com/watch?v=1OeoBbjwEFg

Momentum is the most powerful force known to mankind.

"That's how we've always done it" drives so much of what humans do it's not even funny. Speaking for my own countrymen, we still mint the penny, write checks, wear ties, shake hands, use imperial, speak English, work 40 hours a week, have 2 political parties, tip waitstaff, etc. not because they are objectively the best solutions, but because that's how we've always done it.

Is there somewhere in the U.S. that doesn't use metric?

2L bottles of soda, 2.4L engines, 100m races, 5K runs, 2cc injections, 20 kilo drug busts, 11mm wrenches, M5 screws

It would take work and there's no pressing reason to do it.

I can imagine what it would be like if you told me you went on a 5 mile hike with your 6'6" friend on a 63 degree day. If that was 8km, 2m, and 17 degrees I have much less intuitive sense of what happened. And I don't see much advantage to switching - it doesn't matter which units you use so long as you're consistent within the domain of use.

What's the downside?

I figured it was a cheap form of protectionism. While it makes it harder for exporters it also makes it harder for importers. It helps maintain a separate local tooling and consumable pipeline which helps with war fighting, it probably also makes money for donors. I think the sheer scale of Chinas exports can and has easily overcome that hurdle so the protectionist aspect is now much less relevant.

Please rewrite this post, but in every 10th word, you should swap the letters e and i. Tomorrow rewrite this post, but instead make it every 9th and 10th word.

Ivintually thes well bi feni and iviryoni well undirstand that i and e ari swappid. But thiri well bi a bet of temi to git adjustid wheli that happins.

The US is huge, both geographically and with regards to population. Where would the political will for such a change come from? There is not much domestic desire to do so, and I am guessing few of the immigrants are chomping at the bit to institute the metric system in light of other, more pressing concerns.

... we have better things to spend trillions of dollars on than change a metric based system with another?

Honestly, HN will moan about how much work and how dangerous the stupidest clock or UTC change is but keep proposing to change every unit used by a quarter of the world's economy. Blows my mind.

It's hard for any culture to do anything that is deeply ingrained into its habits. Think of all the things that would have to change everywhere, in everything, when something as basic as a unit system changes.

As seamless language translation becomes ever more integrated into our communications, it will matter less and less what languages, much less measurement system people use.

Reading all the reasoning, both for and against, reminds me that ever since I heard about confirmation bias I see it everywhere. :-)

It's not hard. We just don't care.

The US is very conservative and broad swathes of the population hate "European" ideas.

Once screen producers start advertising their products in metric, the change will come.

Because the benefits of switching seem relatively limited for the cost.

The issue with switching to metric in the US is that there isn't much practical benefit that would offset the downsides. Technically, the US switched to metric a long time ago. No one uses it in their day-to-day life. The US is economically big enough that it can easily sustain using its own standards.

Since there is no practical benefit, most people don't care and aren't going to go to the effort. A vast amount of non-metric physical tooling already exists -- replacing it would be extremely expensive. For things like engineering, it doesn't matter because the units have to follow the values anyway; there are many common unit systems in engineering that are neither metric nor US imperial, and working across unit systems is something you always have to do anyway.

tl;dr: low ROI and high cost to switch

Tribalism and identity politics.

This Johnny Harris youtube video does a decent job describing this. It would take at least a generation before the US population really got used to using metric places.

https://www.youtube.com/watch?v=nRnuY1Vao0o

The timestamp where he's directly talking to what I mean:

https://youtu.be/nRnuY1Vao0o?t=1192

In it, he mentions the main reason why he doesn't use the metric system: he can't. Inches and feet and miles and ounces and pounds are so deeply ingrained in his mind. Even when he tries to relate to metric, its always in relation to imperial units, because to him its not about 30 centimeters its about a foot. Its not about a kilogram, its about two pounds. He can do the conversions in his head usually, but actually visualizing how far 5km is means converting it to miles which he can conceptualize.

Its like learning another language. Sometimes people are really great about just remapping their brain, but many people just end up internally translating things instead of actually deeply adopting the language. And if they're going to just be constantly translating it, it'll just be uncomfortable for them, and they won't want to do it. Because to a certain extent, what's the harm in my speedometer being primarily miles per hour? What's the harm in having a sign say "Rest Stop 5mi" instead of "Rest Stop 8km"?

I'm pretty similar to Johnny here. I can easily visualize ~300mi on a map. 300km? I know it is a good bit shorter than 300mi, but just at a quick off the top of my head I wouldn't quite know how far that really is. I'd be just doing the conversions in my head which takes me a second to think "ok, so divide by 1.6ish, so that's a little over 180 miles..." which I'd then use to conceptualize how far that is.

Changing to metric isn't just changing all the highway signs. Sure, that could be done in just a few years if we wanted to. Its changing how everyone actually thinks, how everyone is actually wired. That's what holds up the US from actually adopting metric.

But in the end, I still do use some metric. This drink I'm drinking has its nutrition label in grams/milligrams/Calories. My child got 1mL of iron supplements and vitamins this morning. It will be a long series of small steps before people get used to the change. Just swapping all the road signs overnight isn't going to lead to very happy people.

Back when most of Europe adopted metric, 40% of the population were illiterate. Tons of people didn't really deal with a lot of weights and measures in their daily lives. We live a very different world today than when metric was adopted in most of the world.

lots of sunk costs. No real interest.

It's political. A significant portion of Americans, mostly conservatives, are unable to accept that anything not invented in the US could be superior to what they are accustomed to.

There was a push toward adopting the metric system under Carter but since then the right wingers have been largely in control of the political discourse.

How can this be strange? I am saying this as a European.

It’s simply customs. And the system works. Why change?

It’s similar like asking why European football clubs wouldn’t want to change to the draft system of the US leagues.

European soccer is commercialized to a degree which is unthinkable for Americans, who are commonly regarded as the bigger capitalists…

The better question to ask is what is the benefit? For everyday usage by regular people, it's not clear to me that metric is superior if you didn't grow up with one or the other, hence the lack of push for a change.

In fact, I've seen the argument made that feet, inches, miles, cups, teaspoon, Fahrenheit, etc are superior to meters, centimeters, km, mL, Celsius, etc for everyday use. As I've seen it presented, this argument contends that centimeters are too small, while meters are too large for many common things you want to measure, such as the height of a person. Likewise cups and teaspoons are actual objects that you could visualize and get a general sense of the amount without even knowing the actual measurement. Same kind of thing for Celsius: the most common usage of temperature measurement for the average person is air temperature. For the set of air temperatures commonly experienced on Earth, Fahrenheit provides more precision.