The only thing that was correct in your link regarding Japanese is "varies".
As for Han characters, Chinese uses those. Japanese uses a mixture of kanji (ancient Chinese characters) and native phonetic characters. So the space needed really depends on the content. As I said before, if it's full of English loanwords (or worse, English technical terminology that's been adopted into Japanese), it'll likely be larger, since all that is expressed in katakana (phonetic characters). If it's something that can be written in mostly kanji, then it'll be quite compact.
Korean does not use Han characters at all. It uses Hangul, an artificial phonetic writing system invented about 100 years ago.
> The only thing that was correct in your link is "varies".
Because I didn't bother to link all guidelines I've found. ;-) Other sources, for example, say that Japanese has a relative contraction of 10% to 55% [1], which is really variable but still supports my claim. There is also an inforgraphic about specific scenarios [2] with a similar conclusion for all CJK languages. It might be possible that some guidelines only show the character count and thus adjusted for the visual space, but I see no reason that most guidelines, primarily from professional translation companies, would get that same point wrong.
> So the space needed really depends on the content. As I said before, if it's full of English loanwords (or worse, English technical terminology that's been adopted into Japanese), it'll likely be larger, since all that is expressed in katakana (phonetic characters). If it's something that can be written in mostly kanji, then it'll be quite compact.
You are correct (I do speak Japanese), but again, the general concensus seems that average Japanese texts do have enough kanjis that make up for some loanwords. I'm well aware that the balance has been greatly changed in recent decades though, so I'd like to be corrected if there is a well-known analysis.
> Korean does not use Han characters at all. It uses Hangul, an artificial phonetic writing system invented about 100 years ago.
Hangul was invented in the 15th century. Only the specific orthographic rules and the current name "hangul" were established ~100 years ago. It took more decades (i.e. circa 1990) for Han characters to be mostly gone from the written Korean, and I observed the final transition as a native Korean speaker.
As for Han characters, Chinese uses those. Japanese uses a mixture of kanji (ancient Chinese characters) and native phonetic characters. So the space needed really depends on the content. As I said before, if it's full of English loanwords (or worse, English technical terminology that's been adopted into Japanese), it'll likely be larger, since all that is expressed in katakana (phonetic characters). If it's something that can be written in mostly kanji, then it'll be quite compact.
Korean does not use Han characters at all. It uses Hangul, an artificial phonetic writing system invented about 100 years ago.