I was in elementary and middle school in the USA during the go metric phase so we spent a lot of time learning about the metric system and converting between different units of measure.
But, in the real world, are most of these units ignored?
For measurement, I’ve only seen centimeters, meters, and kilometers.
For weight, I’ve really only seen grams and kilograms used, although I guess milligrams are used with drug dosages.
For capacity, I’ve only seen milliliters and liters.
Does anyone actually use other metric measurements in daily life? Hectograms, dekaliters, or decimeters?
Most of those units aren’t even needed inside of science, especially since the advent of the SI system.
The SI system uses the following base units: meter for measurement of length, the kilogram for mass, the second for time, the ampere for electric current, the kelvin for temperature, the candela for luminous intensity, and the mole for amount of substance. Note that the base unit for mass is NOT the gram; it is the kilogram. (The gram is defined in the SI system as exactly 1/1000 of a kilogram.)
For measure of length, for example, the SI system uses the meter. There is really no need for centimeters, millimeters, or kilometers in the SI system, much less decimeters. You simply use scientific notation. For example, a measurement of 1250 kilometers would be written as 1.25 x 10[sup]3[/sup] meters. This also allows you to specify the number of significant figures.
The only reason to use the other prefixes is for convenience when working with a given magnitude of measurement. For example, it might be convenient to use nanometers when describing wavelengths of light. Of course, we’re back to science again. Outside of science/technology, people aren’t likely to need to use nanometers.
In the real world, most units of measure are ignored regardless of the system. How often do you use light-years, megatons, barleycorn, furlong, hogshead, bushel, or dram?
Hectare, millimeter and millisecond immediately came to mind. In continental Europe, I’ve seen centiliters used on consumer products and kiloliters, aka cubic meters, used on large storage tanks.
Are you asking about the USA part of the real world, or the rest of it?
In the US, the units you use are:
length: miles, feet, inches
weight: pounds, ounces, tons
volume: gallons, ounces, cubic feet, tablespoons, teaspoons, cups
When’s the last time you used any other unit, metric or otherwise?
Similarly, outside the US people regularly use:
length: kilometers, meters, centimeters, millimeters
weight: kilograms, grams, tons
volume: liters, milliliters, tablespoons, teaspoons, cups
It’s very rare to use any prefixes that aren’t 3 orders of magnitude apart, i.e. you use kilograms or grams, not the ones in between (centigrams and hectograms). Centimeter is the major exception.
By the way, cups, tablespoons and teaspoons are actually metric defined units (250ml, 15ml and 5ml respectively).
Yes, but in the real world people generally use measurements they have an intuitive understanding of, and aren’t needing to apply a conversion to. So I may know that 500 meters is 5 hectometers, but I’d never use that as a unit of measurement. It’s either 500 meters or 1/2 a kilometer. There’s going to be some variation across countries, and also across industries, but just staying within the milli- to kilo- ranges for length, volume and mass, it’s unlikely that anywhere is using all 21 units of measurement.
Deciliters are used in blood tests, as in mg per dL. Also, medical types insist on using cubic centimeters (cc) instead of milliliters like everyone else.
Centilitres are the standard measurement used for wine, at least in the UK and I think Europe generally. I suspect this is because it makes it look a bit different, fancier and seems bigger having ‘70 cl’ written on the bottle rather than ‘700 ml’ or ‘0.7 l’.
I can’t think of the last time I’ve seen a henry, farad, pascal, gauss, or gray used outside of a scientific context. There are a lot of units out there.
Units of centilitres (occasionally decilitres) occur on any old bottle of spirits, as has been noted. Units like candelas, Siemens, teslas, and katals are the type one might imagine less known outside of science.
I hear the word “furlong” mentioned three times a year: the Kentucky Derby, Preakness and Belmont Stakes. I don’t know what a “rod” is.
And whatever anyone thinks a “cord” of wood is, they’re probably wrong. And that country guy who tells you he has a cord of firewood in the back of his pickup, he’s definitely lying.
Back in the day, there were a couple of old engineers who gave me a hard time because I didn’t have the number of feet in a mile or the number of gallons in an acre-foot memorized.
An acre-foot is a measure of water equal to about 326,000 gallons or 43,560 cubic feet or 1233.5 cubic meters. I don’t know if it’s used much any more, as I’ve been out of the big-water-projects loop for a long time.