German with a scientific background. I can deduce the meaning of the words but I’ve never seen them used. I’m not even sure these units of measurement were mentioned when these were discussed. Most stuff is ton, kilogram, gram, miligram, microgram; kilometer, meter, centimeter, milimeter, micrometer. Rarely decimeter are thrown around.

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.

Dekametre and hectometre, rarely. Mostly mm, cm, m, km.

In Europe, hg is relatively common, whereas in Canada, prices for deli products are “per 100 g” instead of per hg.

Also in Europe, cl and dl are common in recipes and bottles of alcohol, but in Canada, almost uniquely mL and L. (And yes, lowercase litre in Europe, but uppercase Litre in Canada, although that’s gradually changing.)

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.

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

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).

Czech republic here: decagram used to weight ham, bacon 🥓 or salami. Usually as “deka” without the gram.

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.

We use litres, which is one decimetre cubed. We use hectares, which is one hectometre squared. But the beauty of it is, that you can just convert everything to units that are more widely understood.

• 1 decimetre = 10 centimetres = .1 metres

• 1 hectometre = 100 metres = .1 kilometre

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.

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

Saying something is 80 meters long is far easier to process than eight decameters.

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.

I’ve seen some obscure uses in technical areas, but in general use no they aren’t used. Metric is better skipping all those and using the thousands prefixes. cm is used but mm is much better. Europe uses cl but we in Canada don’t, we use ml.

Decilitres/centilitres are relatively common, but they’re the only ones that come to mind.