They are “technically correct” measurements since they are a valid prefix, and could be used if you wanted. but they are very infrequently used in any industry. Since most of the time measurements are better served by higher precision (just using Meters) or need no precision at all over long distance (switch to kilometers), no need for excess measurement types unless necessary

Valid, but rarely used, as it’s usually just as fast to say “two hundred meters” instead of “two hecto meters”.

However, those prefixes have other (non-SI) uses. A hectare is common way of referring to a 100x100 meter area. And a decare is 10 ares, i.e. 0.1 hectare.

For distance, no. Day to day we use mm, cm, m and km. But in more specialised settings (e.g. construction) I’ve seen sometimes decameters.

For weight yes, grams, hectograms, kg, tons. Liquids is usually ml, cl, liters, hectoliters (not sure it’s spelt that way).

In labs I’ve also seen also micro and nano of all three units.

No, some measurements just aren’t used, even when they’d be a good fit.

Like lengths. We never use anything above km. Even for things like space, we say “million km” rather than gigametre.

The closest we come to hectometre is hectare, which is used for land area.

In The Netherlands we actually use “hectometerpaaltjes”, which translates to hectometer-signs. They are numbered signs placed on regional roads and highways every 100 meters, which is a hectometer. Although not a direct use of measurement, the term hectometer still is in active use this way.

deleted by creator

In France “hectare” (10 000m²) is used for fields and burning forest. Beside that deca or hectometers are never used

From my experience in Norway, these are typical in context of daily speech:

Weight (gram): tonne (a substitute name for Mg (Mega)), kg, hg, g, mg, μg (mostly in medicine)

Distance (meter): mil (10 km), km, m, dm (kinda rare), cm, mm

Volume (liter): l, dl, cl, ml

In my experience, the deca-predix is very rarely used. Most of the missing prefixes are just substituted for numbers, i.e. saying “a thousand kilometers” is much more common that “a megameter”. Of course, this differs depending on context, as a lot of the prefixes become more common within scientific fields where the sizes are common.

On a separate note, even the numbers can be a bit inconsistent. It has bothered me that it’s often common to say “a thousand milliard” instead of “one billion” (also note that we use the long scale).

As an American who has gotten very used to metric units in studying engineering, the general rule I picked up is that you typically only change units every three orders of magnitude. So 8 decameters would typically be expressed as 80 meters, maybe 0.08 kilometers. Decameters and hectometers are a thing, but they’re not common units. Even centimeters don’t see much use compared to millimeters.

It depends on the situation, sometimes they are really handy but most of the time we stick to kilo, centi and mili.

Where i live, Hecto (100x) is used, for example to measure distances and areas for big properties. 1 hectometro equalls 100 m, or 1 hectarea (hm^2) equals 10000 m^2.

Also, it is widely use for pressure, cause 1 atm is 1013 hPa

Decameters are used but for special situations, like quantifying natural gas consumption

in school in austria we teach dezimeter (tenth of a meter)

Yes, they are used, but typically in specialized applications which is why you don’t see them every day.

In Romania we use them for measuring areas. An “ar” is 100m^2 or a square decameter, and a hectare is a 10000m^2 or a square hectometer.

In America, I’ve seen nurses and diabetics use deciliters in reference to medication or concentration before.

In Italy we use hectograms (“ettogrammi”, “etti” for short) in day to day life when buying groceries. You don’t ask for 200 grams of ham, you just ask for 2 etti.