My argument is mostly for things like day-to-day practical measurements, there's no difference between the two units, so it doesn't affect people.
Temperature – absolutely no difference in _practicality_ in communicating about the daily weather in C or F. People that claim otherwise are usually just arguing for the system they grew up with.
Weight – no difference in measuring most larger weights in pounds vs kgs. (weighing people, furniture, cars, trucks, comparing the weight of laptops, etc)
Distance – Whether DC to NY is 220 miles or 352 kilometers makes no difference.
In most daily use, the differences in units probably don't make any difference to most people, which is why the cost of switching (so that it looks good on paper) just hasn't caught on.
However, in the sciences, in cooking, areas where you need precise measurements, grams, KG, etc all give you nicer units to work with.
When measuring things for DIY and home improvement, God, I wish I could do everything in meters and centimeters than 1/8 or 1/6 of an inch (mainly for doing calculations).
And when cooking, I cringe with "cups" and "tbsp" – I wish it were all grams and ml.
I can't think of any good reason to use volumetric measurement in cooking. Even if you only need approximate measurement, it's still better to use weight because you can put the cooking container directly on the scales and avoid having to wash your measuring cups. And if you do need accuracy, measuring by weight wins every time.
I can't think of any good reason to use volumetric measurement in cooking
A good reason is because you rarely need exact measurements in cooking (vs. baking), and it's easy to eyeball approximate volumetric measurements, especially with help from the known volume of a container; also because many recipes need quantities of some ingredients (most frequently water) that would require a much larger and more expensive kitchen scale than most people would like to keep.
Small quantities under a tablespoon or 10ml by volume can be quite challenging to weigh, and is much easier to fill up a fixed size tsp/tbsp measure. If your ingredient is a commodity and has a known density ahead of time (water, olive oil, salt, whatever) its mechanically simpler. There are also times when you can't measure into your cooking container directly - maybe it's hot.
I would disagree about weight and distances, having multiple of 10 units make computation easy, it is unfortunate that time is different. Though I agree most people this days would maybe avoid calculating things and use a calculator/software1
Temperature - at what temperature does the water freeze? 0C, 32F. At what temperature does the water boil? 100C, 212F. Which ones are easier to remember on a day-to-day basis?
Weight, Distance - conversion is a lot easier in the metric system
You just mentioned that there were no differences, than why would you use units which have strange relations between each other instead of units that are easy to remember, easy to convert are based on math instead of historical/common knowledge?
How often are you boiling and freezing water when deciding what clothes to wear?
Ok so when measuring water freezing, you have a nice 0. But how do you measure hot weather? 30C? 35C? Meaningless numbers, correct?
I am talking about daily weather. Celsius is no more intuitive than Fahrenheit when discussing it.
Even with cooking, when you are around a certain system, you're just used to it.
I bake a cake at 350F, I fry things at 350-400F. 175C is no more practical than 350F. I need to cook meat to at least 140F-160F to kill the bacteria.
The equivalents in Celsius are no easier to remember from a practical standpoint.
Even body temperature, from my understanding, almost everyone uses 98.5F, correct? (At least in India, where everything was KG and KM, people still used to measure body temperature in F).
Well fridge should not go below 0 Celsius or you have trouble. Teach your children that.
When thinking about boiling water it is easier to think how close to it you are in Celsius, 50% if temp is 50 Celsius.
Personally I'm from Europe but live in US and have trouble with weather forecasts in Fahrenheit. They don't make sense especially when it gets cold.
Even IF Celsius and Fahrenheit were equally good for most purposes, it would be easier if every continent used the same system. Why, because people travel, often from continent to continent.
So if we (the people of Earth) should choose we should most probably choose Celsius, even if it were just slightly better than Fahrenheit.
Well fridge should not go below 0 Celsius or you have trouble
There are things in the world other than fridges.
When thinking about boiling water
I only really do this about 1% of the time I need to use temperature.
Even IF Celsius and Fahrenheit were equally good for most purposes, it would be easier if every continent used the same system. Why, because people travel, often from continent to continent.
This is really the only reason to use Celsius: it works well with other things.
Sure, my point was that the unit of measurement for body temperature in many places that use metric is probably still Fahrenheit, not Celsius. (And that it doesn't really hurt anything, since the boiling and freezing point of water is irrelevant in checking whether a human is ok or not)
Seriously you don’t see any difference in defining hot weather as 1/3 of the boiling temperature of water?
Try to do that in Fahrenheit and you have to do something crazy like (212 - 32) / 3 + 32, and I’m not even 100% sure that is correct...
And I guess that for you is much better to remember that at 32 F is very dangerous to drive outside rather than at 0. I really can’t understand how can someone would advocate for maths gimmicks when you have a much easier solution that is even an international standard (or to be precise it’s extremely easy to convert to and from that standard)
"1/3 of the boiling temperature of water" is just as arbitrary as "32".
Generally speaking, you get freeze warnings and black ice warnings when necessary instead of checking to see whether or not the current temp is literally below the freezing point of water. I think OP was just saying that it's good enough for a layperson to use day-to-day.
At what temperature does the human body rest? ~100F. At what temperature is frostbite a concern to uncovered skin? ~0F. I feel like these benchmarks are more useful in my day to day life than water temps.
Yup, that’s one of my favorite things about the Fahrenheit scale: it’s a good approximation of “on a scale of 1-100, how cold/hot is it outside?” where a broad range of human climates would agree on the answer.
0F is pretty dang cold out, and 100 is pretty dang hot out. Sure, there are temperatures in human habitats outside that range, but most people would consider then “extreme” temperatures, hence values less than zero, or greater than 100.
The water freezing/boiling point calibration points seem interesting until you realize that you're never actually at 1 atmosphere (due to elevation and weather) or working with pure water.
Regarding temperature, Fahrenheit offers more granularity. I, for one, can definitely perceive the difference between 22, 22.5, and 23 degrees C (71.6, 72.5, and 73.4 degrees F, respectively), but on a typical metric thermostat, fractions of a degree aren't allowed.
Until hardware stores in the US start stocking measuring devices longer than a foot with cm and mm markings, I'm going to disagree with the DIY aspect. Yes I can use a tape measure or buy one online. Discussing lumber here is always inches even when precision is necessary, still inches. It's all very frustrating imo.
Yes it is. I bought a tape-measure maybe part of a tool-kit or something and lo and behold it is ONLY in inches. It could easily have cm on the other side but it doesn't.
I guess its cheaper to produce a one-sided measuring tape.
Look at my arguments. I'm saying exactly what you're saying. Areas that need precise measurements (especially the sciences) are already using metric. I also prefer metric when cooking.
However, think of it this way: In conversational transfer of information, it makes zero difference. If I'm telling you something is 300 miles away, it isn't more useful for me to tell you it's 480 kilometers away. What extra information do you get from that? That it's 480,000 meters away? Humans can't properly visualize probably more than 100 meters. So what practical use when calculating driving distance is knowing that Kilometers vs meters the distance is?
You are making a distinction between daily use and specialist use and then suggesting it doesn't matter, I suppose because everyone has a daily use.
Day-to-day using miles or inches for distance, gallons for volume, and now we have specialists using miles-per-gallon for fuel efficiency, cubic inches for stroke volume ...
I have no idea how you'd convince a large country to convert to SI aside from just forcing it. There are quantifiable upsides (consistency, conversion, not needing two sets of tools, etc) but momentum is hard to overcome.
Interestingly Metric is "the preferred system of weights and measures for United States trade and commerce" according to the 1975 Metric Conversion Act[0]. But it had no teeth, so everyone just continued using US Customary Units.
Yup this is what I always tell people – in the US, all science is taught in Metric. (at least in my schooling in the DC area). All physics, chemistry, etc units were in metric. So where it truly makes a difference, it seems to all be metric.
That's why I'm always surprised when I read a story about some scientific endeavor in the US that didn't use metric.
Don't you think that weight (or, pedantically, mass) generally makes more sense for many ingredients? 100g of flour is a well-defined quantity, one cup of flour can vary significantly depending on how tightly packed the flour is.
The packing is mostly a function of how you yourself put the flour into the cup/how it was handled and stored before I got to my house. In practice there's not much variation of this sort. And you still want to taste and adjust as needed, so I don't think you would really need to-the-gram precision since there are so many factors like humidity that can impact how much of an ingredient you should use anyways.
I think the way it'll happen is by America's loss of manufacturing. That's a big user of units and it's declining. Imported stuff is going to be more and more often metric unless it was also designed in America. So people are going to encounter it more and more. At some point, there might be a price penalty for specifying the less common imperial threads and material thicknesses on Chinese made parts so American designers in competitive industries might start preferring metric.
But it might never go away from daily life. The Chinese still use "jin" as a unit of weight/mass. The communists unified the customary definitions to be exactly 0.5 kg, but even they weren't powerful enough to force everybody to use kg directly. If a communist dictatorship is too weak, there's no hope for a democratic government!
Funfact: US customary units are metric by definition. Everything is in grams and meters and liters, it’s just using weird numbers so it roughly fits with customary units roundedly.
The switch happened in 1893 according to wikipedia.
When you get right down to it, it's still just arbitrary stuff that amounts yo "about yay long", "about yay heavy", and so forth... but with a means of describing what we mean to people (or whatever they choose to call themselves) who aren't present and have no access to an official artifact. The metre is about a cloth yard (a very old "standard") with an excuse (one ten-millionth of the distance from the north pole to the equator through the Paris meridian... or thereabouts; we should really work on a better way of defining that at some point), the litre is close enough to a compromise quart, which can be sort of defended by monkeying with the metre (hey, a decimetre's about a hand, right? Clever of us to have thought of that), and the kilogram's a bit too big and the gram's a bit too small, but you can't get 'em all right all of the time. Defining them all in a way that doesn't rely on artifacts and/or special moments in time is a good idea, but it doesn't make them any less arbitrary. There is nothing fundamentally more scientific about SI.
Base-12 is a wonderful number system. 12 is divisible 2,3,4 and 6. What's 10 divisible by? 2 and 5. In an ideal society, maybe they'd use a kind of metric base-12 system.
That'd offer the best of both inches/feet and the simplicity of the metric system's scaling.
Now that you mention it, I suppose one of my favorite things about inches are their base-2 subdivisions (e.g. 16ths). The orders of magnitude aren't nearly as drastic as with base 10. They're much more intuitive and easier to estimate visually.
Fractions are great for mental math, especially division, in situations where you might be working with wood for example.
6 months of carpentry made me appreciate feet and inches in a new way.
If you ignore the thumbs, each finger has 3 subsections, so in total you have 12 "slots" on your hand. And you can use them to count with the spare thumb. It's even more convenient than counting on fingers because you're only using one hand, and the other one is free!
Customs stick around for a long time, but I think metric will gradually find its way in, it will just take generations. When I for example look into discussions about hiking and outdoor life right now, there is a mix of units being used conventionally - US customary and metric depending on what quantity is being measured. And this is a good thing, it mean the metric units are creeping in, and some people are getting used to them. Even if it's not a full conversion.
If I'm placing bets, the liter will be the metric unit to take over next in the USA (winning out over gallon and fl. oz), maybe just because the gallon has a good size, not too small or too large - stuff you buy liquid is often around 0.5 - 2 liters.
What will make the change easier is smartphones, smart-phone measuring stick can tell you cm. I haven't seen one but I assume a smartphone could also be used to measure weight?
In many private industries where it matters in the US, they've switched over to metric/are increasingly moving over to it/using it side-by-side with imperial units. The biggest hurdles are all levels of government and the massive cost of converting all measurements over to metric. And given how much we already neglect public infrastructure, I don't see changing to metric units happening any time in the next several decades.
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Seems like a positive change. But somehow (perplexingly) we still use inches, feet and miles in a major part of the world.
My argument is mostly for things like day-to-day practical measurements, there's no difference between the two units, so it doesn't affect people.
Temperature – absolutely no difference in _practicality_ in communicating about the daily weather in C or F. People that claim otherwise are usually just arguing for the system they grew up with.
Weight – no difference in measuring most larger weights in pounds vs kgs. (weighing people, furniture, cars, trucks, comparing the weight of laptops, etc)
Distance – Whether DC to NY is 220 miles or 352 kilometers makes no difference.
In most daily use, the differences in units probably don't make any difference to most people, which is why the cost of switching (so that it looks good on paper) just hasn't caught on.
However, in the sciences, in cooking, areas where you need precise measurements, grams, KG, etc all give you nicer units to work with.
When measuring things for DIY and home improvement, God, I wish I could do everything in meters and centimeters than 1/8 or 1/6 of an inch (mainly for doing calculations).
And when cooking, I cringe with "cups" and "tbsp" – I wish it were all grams and ml.
I can't think of any good reason to use volumetric measurement in cooking. Even if you only need approximate measurement, it's still better to use weight because you can put the cooking container directly on the scales and avoid having to wash your measuring cups. And if you do need accuracy, measuring by weight wins every time.
A good reason is because you rarely need exact measurements in cooking (vs. baking), and it's easy to eyeball approximate volumetric measurements, especially with help from the known volume of a container; also because many recipes need quantities of some ingredients (most frequently water) that would require a much larger and more expensive kitchen scale than most people would like to keep.
Small quantities under a tablespoon or 10ml by volume can be quite challenging to weigh, and is much easier to fill up a fixed size tsp/tbsp measure. If your ingredient is a commodity and has a known density ahead of time (water, olive oil, salt, whatever) its mechanically simpler. There are also times when you can't measure into your cooking container directly - maybe it's hot.
I would disagree about weight and distances, having multiple of 10 units make computation easy, it is unfortunate that time is different. Though I agree most people this days would maybe avoid calculating things and use a calculator/software1
Temperature - at what temperature does the water freeze? 0C, 32F. At what temperature does the water boil? 100C, 212F. Which ones are easier to remember on a day-to-day basis?
Weight, Distance - conversion is a lot easier in the metric system
You just mentioned that there were no differences, than why would you use units which have strange relations between each other instead of units that are easy to remember, easy to convert are based on math instead of historical/common knowledge?
How often are you boiling and freezing water when deciding what clothes to wear?
Ok so when measuring water freezing, you have a nice 0. But how do you measure hot weather? 30C? 35C? Meaningless numbers, correct?
I am talking about daily weather. Celsius is no more intuitive than Fahrenheit when discussing it.
Even with cooking, when you are around a certain system, you're just used to it.
I bake a cake at 350F, I fry things at 350-400F. 175C is no more practical than 350F. I need to cook meat to at least 140F-160F to kill the bacteria.
The equivalents in Celsius are no easier to remember from a practical standpoint.
Even body temperature, from my understanding, almost everyone uses 98.5F, correct? (At least in India, where everything was KG and KM, people still used to measure body temperature in F).
Well fridge should not go below 0 Celsius or you have trouble. Teach your children that.
When thinking about boiling water it is easier to think how close to it you are in Celsius, 50% if temp is 50 Celsius.
Personally I'm from Europe but live in US and have trouble with weather forecasts in Fahrenheit. They don't make sense especially when it gets cold.
Even IF Celsius and Fahrenheit were equally good for most purposes, it would be easier if every continent used the same system. Why, because people travel, often from continent to continent.
So if we (the people of Earth) should choose we should most probably choose Celsius, even if it were just slightly better than Fahrenheit.
There are things in the world other than fridges.
I only really do this about 1% of the time I need to use temperature.
This is really the only reason to use Celsius: it works well with other things.
98.6 is the approximation most people memorize in Fahrenheit. That number implies more precision than you can reasonably assume in practice, however.
Sure, my point was that the unit of measurement for body temperature in many places that use metric is probably still Fahrenheit, not Celsius. (And that it doesn't really hurt anything, since the boiling and freezing point of water is irrelevant in checking whether a human is ok or not)
Seriously you don’t see any difference in defining hot weather as 1/3 of the boiling temperature of water? Try to do that in Fahrenheit and you have to do something crazy like (212 - 32) / 3 + 32, and I’m not even 100% sure that is correct... And I guess that for you is much better to remember that at 32 F is very dangerous to drive outside rather than at 0. I really can’t understand how can someone would advocate for maths gimmicks when you have a much easier solution that is even an international standard (or to be precise it’s extremely easy to convert to and from that standard)
In Fahrenheit, hot is 100 and cold is 0.
In Celsius, hot is 30 and cold is -10.
When talking about it for what you're wearing and subjective experience, Celsius is a little more awkward and compressed.
Sure, scientifically celsius is more useful, but how often does that overlap with the weather?
No, cold is 0 in Celsius. You risk your life in icy roads at 0.
This comparison is utterly meaningless to me, and I say this as someone who prefers to use Celsius.
"1/3 of the boiling temperature of water" is just as arbitrary as "32".
Generally speaking, you get freeze warnings and black ice warnings when necessary instead of checking to see whether or not the current temp is literally below the freezing point of water. I think OP was just saying that it's good enough for a layperson to use day-to-day.
At what temperature does the human body rest? ~100F. At what temperature is frostbite a concern to uncovered skin? ~0F. I feel like these benchmarks are more useful in my day to day life than water temps.
Yup, that’s one of my favorite things about the Fahrenheit scale: it’s a good approximation of “on a scale of 1-100, how cold/hot is it outside?” where a broad range of human climates would agree on the answer.
0F is pretty dang cold out, and 100 is pretty dang hot out. Sure, there are temperatures in human habitats outside that range, but most people would consider then “extreme” temperatures, hence values less than zero, or greater than 100.
That is pretty subjective and no better than Celsius. Anything below 30F is pretty dang cold for me and anything above 85F is too hot
You mean at what temperature does water freeze at sea level, right? Pure water, I mean, not normal tap water.
Or, you know, just keep the freezer cold enough to take care of it regardless.
The water freezing/boiling point calibration points seem interesting until you realize that you're never actually at 1 atmosphere (due to elevation and weather) or working with pure water.
The old British system is good for one thing: tea. Want to brew some tea? 1 teaspoon per cup.
Regarding temperature, Fahrenheit offers more granularity. I, for one, can definitely perceive the difference between 22, 22.5, and 23 degrees C (71.6, 72.5, and 73.4 degrees F, respectively), but on a typical metric thermostat, fractions of a degree aren't allowed.
Until hardware stores in the US start stocking measuring devices longer than a foot with cm and mm markings, I'm going to disagree with the DIY aspect. Yes I can use a tape measure or buy one online. Discussing lumber here is always inches even when precision is necessary, still inches. It's all very frustrating imo.
Yes it is. I bought a tape-measure maybe part of a tool-kit or something and lo and behold it is ONLY in inches. It could easily have cm on the other side but it doesn't.
I guess its cheaper to produce a one-sided measuring tape.
"day-to-day practical measurement" as distinct from what?
Theoretical physicists might be able to skip the units, but the rest of us farmers, engineers, cooks, are doing something practical when we measure.
I'm not really sure what you are arguing.
Look at my arguments. I'm saying exactly what you're saying. Areas that need precise measurements (especially the sciences) are already using metric. I also prefer metric when cooking.
However, think of it this way: In conversational transfer of information, it makes zero difference. If I'm telling you something is 300 miles away, it isn't more useful for me to tell you it's 480 kilometers away. What extra information do you get from that? That it's 480,000 meters away? Humans can't properly visualize probably more than 100 meters. So what practical use when calculating driving distance is knowing that Kilometers vs meters the distance is?
You are making a distinction between daily use and specialist use and then suggesting it doesn't matter, I suppose because everyone has a daily use.
Day-to-day using miles or inches for distance, gallons for volume, and now we have specialists using miles-per-gallon for fuel efficiency, cubic inches for stroke volume ...
"tsp", that's tablespoons, right? Teaspoons? Argh!
Tsp is teaspoon; tb/tbl/tbsp is tablespoon
tsp (or just t) is teaspoon, Tbsp (or TB, Tbl, or just T) is tablespoon. The little one has a little t, the big one has a big T.
Except in science. Where the inconsistency itself can cause problems:
https://en.wikipedia.org/wiki/Mars_Climate_Orbiter#Cause_of_...
I have no idea how you'd convince a large country to convert to SI aside from just forcing it. There are quantifiable upsides (consistency, conversion, not needing two sets of tools, etc) but momentum is hard to overcome.
Interestingly Metric is "the preferred system of weights and measures for United States trade and commerce" according to the 1975 Metric Conversion Act[0]. But it had no teeth, so everyone just continued using US Customary Units.
[0] https://en.wikipedia.org/wiki/Metric_Conversion_Act
Yup this is what I always tell people – in the US, all science is taught in Metric. (at least in my schooling in the DC area). All physics, chemistry, etc units were in metric. So where it truly makes a difference, it seems to all be metric.
That's why I'm always surprised when I read a story about some scientific endeavor in the US that didn't use metric.
The US uses some metric units for some liquids (e.g. a 2 liter of soda).
For me a big stumbling block is cooking; I like using volume units for cooking, but metric recipes tend to use weight.
Don't you think that weight (or, pedantically, mass) generally makes more sense for many ingredients? 100g of flour is a well-defined quantity, one cup of flour can vary significantly depending on how tightly packed the flour is.
The packing is mostly a function of how you yourself put the flour into the cup/how it was handled and stored before I got to my house. In practice there's not much variation of this sort. And you still want to taste and adjust as needed, so I don't think you would really need to-the-gram precision since there are so many factors like humidity that can impact how much of an ingredient you should use anyways.
Why not use liters?
I think the way it'll happen is by America's loss of manufacturing. That's a big user of units and it's declining. Imported stuff is going to be more and more often metric unless it was also designed in America. So people are going to encounter it more and more. At some point, there might be a price penalty for specifying the less common imperial threads and material thicknesses on Chinese made parts so American designers in competitive industries might start preferring metric.
But it might never go away from daily life. The Chinese still use "jin" as a unit of weight/mass. The communists unified the customary definitions to be exactly 0.5 kg, but even they weren't powerful enough to force everybody to use kg directly. If a communist dictatorship is too weak, there's no hope for a democratic government!
Probably something to do with this type of propaganda... https://www.reddit.com/r/cringe/comments/bxugvv/a_fox_news_s...
Funfact: US customary units are metric by definition. Everything is in grams and meters and liters, it’s just using weird numbers so it roughly fits with customary units roundedly.
The switch happened in 1893 according to wikipedia.
https://en.m.wikipedia.org/wiki/United_States_customary_unit...
When you get right down to it, it's still just arbitrary stuff that amounts yo "about yay long", "about yay heavy", and so forth... but with a means of describing what we mean to people (or whatever they choose to call themselves) who aren't present and have no access to an official artifact. The metre is about a cloth yard (a very old "standard") with an excuse (one ten-millionth of the distance from the north pole to the equator through the Paris meridian... or thereabouts; we should really work on a better way of defining that at some point), the litre is close enough to a compromise quart, which can be sort of defended by monkeying with the metre (hey, a decimetre's about a hand, right? Clever of us to have thought of that), and the kilogram's a bit too big and the gram's a bit too small, but you can't get 'em all right all of the time. Defining them all in a way that doesn't rely on artifacts and/or special moments in time is a good idea, but it doesn't make them any less arbitrary. There is nothing fundamentally more scientific about SI.
Base-12 is a wonderful number system. 12 is divisible 2,3,4 and 6. What's 10 divisible by? 2 and 5. In an ideal society, maybe they'd use a kind of metric base-12 system.
That'd offer the best of both inches/feet and the simplicity of the metric system's scaling.
Base-16 would've been more useful imho, from a computer science perspective :)
What does one need fractions for actually? You can measure with digits behind the point.
I find 3.5 and 4.6 easier to compare then 7/2 and 23/5.
Now that you mention it, I suppose one of my favorite things about inches are their base-2 subdivisions (e.g. 16ths). The orders of magnitude aren't nearly as drastic as with base 10. They're much more intuitive and easier to estimate visually.
Fractions are great for mental math, especially division, in situations where you might be working with wood for example.
6 months of carpentry made me appreciate feet and inches in a new way.
You have (probably) 10 fingers, thus base 10.
If you ignore the thumbs, each finger has 3 subsections, so in total you have 12 "slots" on your hand. And you can use them to count with the spare thumb. It's even more convenient than counting on fingers because you're only using one hand, and the other one is free!
wouldnt base 11 make more sense then?
Customs stick around for a long time, but I think metric will gradually find its way in, it will just take generations. When I for example look into discussions about hiking and outdoor life right now, there is a mix of units being used conventionally - US customary and metric depending on what quantity is being measured. And this is a good thing, it mean the metric units are creeping in, and some people are getting used to them. Even if it's not a full conversion.
If I'm placing bets, the liter will be the metric unit to take over next in the USA (winning out over gallon and fl. oz), maybe just because the gallon has a good size, not too small or too large - stuff you buy liquid is often around 0.5 - 2 liters.
I'd bet a Troy ounce of feathers we just end up dual-stack forever.
What will make the change easier is smartphones, smart-phone measuring stick can tell you cm. I haven't seen one but I assume a smartphone could also be used to measure weight?
AFAIK imperial units are defined in terms of SI units.
Since 1959: https://en.wikipedia.org/wiki/International_yard_and_pound
In many private industries where it matters in the US, they've switched over to metric/are increasingly moving over to it/using it side-by-side with imperial units. The biggest hurdles are all levels of government and the massive cost of converting all measurements over to metric. And given how much we already neglect public infrastructure, I don't see changing to metric units happening any time in the next several decades.
I think it depends on how you define major part...
Burma, Liberia, and the US are the only countries in the world that have not adopted the International System of Units
http://blog.sciencescore.com/blogss_uploads/All-about-Metric...
Imperial: USA, Canada, UK, India. Metric: The rest (190~ other countries).
Imperial: USA, Liberia
Burmese: Myanmar
Metric: ~200 other
"Major", i.e. three countries in the world.