The situation is far more bizarre than "use" or "not use." As I understand it, America uses something along the lines of "converted metric units" - i.e. the entire imperial system is defined according to metric/SI. Some subset of public records have been, supposedly, converted to metric. If you have a recent car, it should have km/h alongside mph (in a smaller font, or as a different digital readout). You'll find metric all over the place if you keep an eye out for it.

US cars have had dual speedometers for decades. One example: https://www.ebay.com/itm/NOS-1980-1981-FORD-MUSTANG-85MPH-SP...

It's called "US Customary", not "imperial".

Only in the US - except for gallons/fluid ounces - those genuinely are US only

No, that's my point. The system of units that is used in the United States is not "Imperial", it has differences from Imperial. We use "US Customary".

We are. All of the US standards are based on metric units. A large number of the products that we buy are made from metric components such as screws. CAD software and machine tools can switch effortlessly between unit standards. There are some standards that are so unique that they might as well be arbitrary, such as spark plug threads.

Some building materials still have US dimensions, but if you measure plywood carefully, it's thicknessed in mm. And the "2 x 4" has never been 2 x 4 inches.

So I think we've made great progress towards an age when units of measure don't matter much any more.

> the "2 x 4" has never been 2 x 4 inches.

Well, it used to be pretty close, until lumber manufacturers and builders cheaped out. They've been gradually "shrinkflating" by reducing the thickness, conveniently requiring less wood. This went along with the switch to fast-growing garbage pine. I lived for a long time in an early-fifties house, and the quality of the wood was vastly superior to what you'd find today. Though, the newer measurements did make things a pain.

No the difference is that we process wood now. Look up dimensional lumber. Its confusing, but makes sense if looked at historically. Iy is not shrinkflation or any other such nonsense.

While i don't doubt they're cheating it a bit, the dimensions originally refered to rough cut, pre-dried lumber. Most of the difference came from finish cuts and drying.

My house was built in 1860. The 2x4s are basically 2x4.

Yeah, I went through a remodel and dealt with the same thing, trying to get drywall to line up on old (1970) and new walls. There's more to it than that, but it's the quick version.

On the other hand, if you find a smaller mill, usually the ones specializing in hardwood, you can still get "full size" cuts, usually without even asking.

My house was built in 1962, and there were some exposed studs, and spares made into things like garage shelves. The old 2x4's are bigger than new 2x4's.

Here in NZ when we switched to metric nothing changed, 2x4s (well we call the 4x2s) were never quite 2x4, and 50x100s (the metric replacement) are close enough (but still not quite) that nothing really changed

four buh two

Back in the 90s, new construction for the US Govt was supposed to all be done using the metric standard even though all of the supplies were in US/Imperial units. Can't imagine the headaches that caused.

Source: My uncle who is/was a contractor

The Comanche helicopter was subject to this dictum. The original drawings specified all metric fasteners. They found out nobody supplies aircraft grade metric bolts so everything had to be redesigned for the next size up in freedom-units with a corresponding weight penalty.

They are using metric:

https://geodesy.noaa.gov/INFO/Policy/files/SPCS2022-Policy.p...

> The meter is the unit of the defining linear parameters for SPCS2022

> SPCS2022 coordinates are published in meters

83 was also defined in metric, but most states chose to use feet for their actual grid.

think renaming a software library is hard? try changing units of measure!!!!!

I think that's what they did in Canada and it worked out great as far as I can tell (except that they had a silly clock based on 10 hours instead of 12 IIRC which had little to do with metric units and nobody wanted it nor was it compatible with the rest of the world).

I once tried to imagine a metric time system, with a deciday of 14.4 minutes. I realized that it would never catch on, because a half-hour TV show would have to be cut to 28.8 minutes losing at least 2 commercials.

They actually tried this, during the French Revolution:

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

It didn't catch on then either.

And again in the 90s https://en.wikipedia.org/wiki/Swatch_Internet_Time

14.4 minutes is a centiday btw. For decimal time I think milliday is the most reasonable unit, being very close to conventional minute.

In practice Mars might be the best opportunity for enacting decimal time, because Earth based units would be bit awkward on Mars.

Thanks for the correction.

I suppose it depends on what your goals are; despite being officially metric, my Canadian and British friends still seem to exhibit a melange of imperial and metric in everyday life.

I notice sometimes when watching British television that stones are commonly used as a unit of weight, which is interesting because it's imperial, not metric, but I've seen never it used in American contexts.

“1 stone equals 14 pounds” is (also) British. It dates back to Edward III (1350). See https://en.wikipedia.org/wiki/Stone_(unit)#England.

The idea to use physical stones as reference weights is way older.

That's because we don't use the Imperial system. The system we use is called "US Customary".

Some metric units work well, and are scaled to human everyday measurements, and some are not.

But the time thing goes to show the absurdity of people's frame of reference. The same people that judgingly ask why the US hasn't gone full metric will say how absurd the idea of base 10 time is.

Saw this here somewhere previously: Sweden did something more insane: Högertrafikomläggningen. Do it once, get it over with?

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

What would the cost be to change everything for a country the size of the USA? I imagine it would be in the trillions.