This sentence on NHK's Easy News got me wondering:


It is shaped like a U and is about 1 km in diameter.


At this website


I found いっきろ

but shouldn't it be


or possibly even


As always in language learning, there is little point for a learner in trying to think about what the correct answer to this question should be; one just needs to know what native speakers do.

Here are three more examples from Jim Breen's wwwjdic:


It was less than one kilometer to the village post office.


There is a bridge about one kilometer up this river.


A gas station is one kilometer ahead.

(As always, the wwwjdic does not provide readings)

  • 3
    I might say じゅういっきろ for 11km, but never いっきろ for 1km. For me, it’s always いちきろ.
    – aguijonazo
    Aug 26, 2021 at 10:05
  • @aguijonazo Oh, is that so? I feel いちきろ and いっきろ sound equally natural.
    – naruto
    Aug 29, 2021 at 6:30

1 Answer 1


The standard way to write 1 km in kana is いっキロ, いっキロメートル, いちキロ or いちキロメートル. Since キロ(メートル) is a loanword from English, it should be written in katakana.

That site (wasabi-jpn) seems to have chosen the all-hiragana style in that page because kana is used like pure phonetic symbols. I guess they thought switching the types of kana depending on the origin of the words may be distracting for beginners when they want to focus only on the pronunciation. They could have chosen the all-katakana style as well. But this is a rather exceptional case where all-hiragana or all-katakana is permitted.

  • Small addition: Also km/s and kilograms are shortened to キロ.
    – a20
    Aug 26, 2021 at 11:33

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