I'm working on a program that convert numbers written in kanji into their arabic numbers counterparts and one of the text I've been given to test my program contains numbers written in katakana. Most of these numbers are small decimals or version numbers (ジュリウスサンテンイチ=>ジュリウス3.1 or ニーテンニメガ=>2.2メガ for example) so they are easy to convert but there are also bigger numbers (like センサンビャクジュッテンイチナナ=>1310.17) which doesn't seem very natural to me, given how long it is to write.

I have implemented something that converts small numbers written in katakana (decimals up to ten) but implementing something that convert every numbers written in katakana would take a long time and I'm wondering if this is worth the hassle because it does seem unlilely to me that people would write big numbers in katakana. My deadline is close so I'd rather spend my time on something more useful.

What do you guys think?

  • 1
    Having numbers written in katakana seems rare to me. I don't think I've ever really seen it beyond 1-10, and even then it was written in katakana for emphasis. However, I also reserve the right to be wrong, since math terminology/practices weren't really a central focus of mine while I was learning the language.
    – ajsmart
    Commented Aug 12, 2021 at 14:40
  • Some systems use katakana to represent readings of certain fields and those fields may contain numbers. Your sample data may have been taken from such a system. Otherwise, it is not common to use katakana to write numbers. Whether or not to support that feature seems to depend on the purpose of your program.
    – aguijonazo
    Commented Aug 13, 2021 at 8:19

1 Answer 1


You usually don't write numbers in katakana regardless of whether it's big or small.

As an exception, katakana may be used for educational purposes to indicate how to pronounce numbers, but hiragana is normally preferred for this purpose. Besides, some proper names derived from "code numbers" have been traditionally written in katakana. For example, D51's nickname is デゴイチ, and Nintendo 64 was sometimes written as ニンテンドーロクヨン in katakana.

Anyway, if you are told to "convert numbers written in kanji into their arabic numbers" but was given tests written in katakana, what you need to do is to contact your client and clarify the requirements.

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