How do Americans refer to their non-metric system in everyday circumstances?
In Australian English, we'd refer to using feet, inches, pounds, ounces and the like as "imperial units". In everyday conversation, do Americans refer to their non-metric units as "imperial", even though it's slightly different to the non-metric units Australians use? If not, what do they use?
In day to day conversations our system of units and measures are not called any thing. We don't have different conversions happening between systems, in most cases, and for us it just makes sense.
For a simple example there are 3 feet in a yard. But we never really do that conversion. It would be far more likely for me to ask for 99 feet of foo, than to try to ask for either 99 feet or 33 yards.
Same for cooking measures. We can convert cups to quarts to gallons and all, but usually we never have to. (and I think this is one of the more common conversions)
The only really common conversion that we do daily, is feet to inches. Even that is not really true, for a lot of people. If you try to buy window blinds for example, you measure with a measuring tape and record the inches, then in the store you shop by inches. Even if its 72 inches, that's still fine.
Having to convert from say feet to meters is extremely rare (on a large scale). If there are professions or common needs that require a lot of conversion there are charts, slide rules, and other aids. But even in those situations (most of the time) the metric units are the foreign ones.
Because we don't go around converting units very much, we really don't have a name for our set of units. There are some names that are in use when comparing the two systems of measures. (Please note these are generalizations)
Probably the most common is when working on cars and other such. Bolts and sockets, wrenches are either SAE (Society of Automotive Engineers) for US built cars, or Metric everywhere else.
Second to that is probably SI. For scientific things, including medicine, chemistry, experiments, etc. SI is used. But almost exclusively. So there are no "Customary Units" in use, most of the time.
When going over historic documents Imperial is some times used. It is also used incorrectly to contrast metric v.s. Imperial. But it's very important to note that US units of measure are not the same as Imperial units, and in some cases (most modern ones) Imperial is used incorrectly.
Customary, Traditional, and Standard terms are generally used in conversations that compare the two systems of measurements. But it can really depend on what circles you run in, which term you would use.
And finally, American is used frequently when asking someone to convert SI units to something more locally useful. "He was about 3 meters tall." "What's that in American?" "Almost 10 feet!"
As an aside, "Freedom Units" are a joke on "Freedom Fries" and are usually mentioned with scorn and laughter. I can't think of anyone that actually uses that term seriously.
So in day to day use I would say we just call them weights and measures. If we are comparing them to SI units then we may use a name, but that name is, in itself, not really standardized. The official standard name is United States customary system or United States customary units but that's almost as rarely used as "Freedom Units" (though "customary units" is a bit more common).
If one is buying tools, for example, one would say: "I need standard measurement - not metric."
I remember the push, when I was a child, to adopt the "metric system", and it just didn't take root. Americans of my generation (tail-end boomer) are fiercely protective of our inches, feet and yards, and think of it as "standard" (as opposed to that foreign "metric" baloney).
In the CAD system that I use, there is a choice between using millimeters or inches as the basic unit of length. The menu asks the user to choose "Metric" or "English" units. The software was originally developed by US folks, and apparently "English" was the word that they expected their users to understand most easily.
When I was in school in the 90s. I was taught these are called customary units.
From Wikipedia:
United States customary units are a system of measurements commonly used in the United States.
The United States customary system (USCS or USC) developed from English units which were in use in the British Empire before the US declared its independence.
Since the question asks for "everyday usage of Americans", I'm going to relax my usual standards of evidence for answering and just respond as an everyday American.
We don't refer to it by any name, usually.
There isn't much call for a name for the collection of units, any more than there's a call for the a name for the specific set of species of US coins¹:
- penny
- nickel
- dime
- quarter
Or the set of Dunkin Donuts cup sizes:
- small
- medium
- large
- extra-large
Or set of Starbucks cup sizes:
- short
- tall
- grande
- venti®
- trenta®
Or the set of Biblically-themed wine bottle sizes:
- standard
- magnum
- double magnum
- jeroboam
- imperial
- salmanazar
- balthazar
How would you refer to these systems, as systems?
You wouldn't. Practically speaking, because there's very little call to talk about them as systems at all (as fish have little call to talk about water), but more fundamentally, that's just the way it is, even if in theory there are other options.
Having said that, when speaking of the American system of units specifically in the context of contrasting it with the metric system, I've sometimes heard it called the Imperial system, though that's technically inaccurate².
¹ Yes, there are 50¢ and $1 coins, but no, nobody uses them.
² The technically accurate name for the system is "US Customary Units", though I doubt 1 person in 100 off the street would even know that, much less ever have call to mention it.
PS: My sister-in-law is French, and she finds the American unit system primitive and confusing. She often (too often ;) wonders aloud how we even remember the relation of one unit to another.
I happened to be in London the other week, and in a free moment toured the Tower of London and snapped this pic of the prototypical set of Imperial units of volume, and sent her a text which read:
See? Easy! All you have to do is get yourself a set of these ;)