Using Arabic numbers in horizontal writing of Japanese

I am working on a translation of a document to Japanese. I have been advised to use Arabic numerals in a text of Japanese when the sentences are written horizontally. For example, 一つ written horizontally should be 1つ. I am wondering to what extent I should use Arabic numerals in the Japanese text, when 1, 2, 3 etc numbers should be used instead of 一、二、三、etc.

Should I replace 一人 with 1人 and 一人一人 with 1人 1人? Similarly, should I replace 一 with 1 in 一度、一部、一番、第一、一枚、一目、一世代、一年、一員、一節、一列目、一歩、一文、一方?

The advice of the forum would be appreciated.

This is a good topic, but I'm not sure if there is a simple, satisfying answer.

For pure numerical expressions (like mathematical equations or financial statements or weights and measures, etc.) I would use arabic numerals when writing horizontally (but its OK to use kanji numerals as long as its comprehensible to the reader). For Japanese expressions (hitomebore, hitori-hitori) I would use kanji, but certainly some of those words you mentioned can be expressed in arabic without any harm （１人、１枚, １年, etc.). The same can't be said for every expression, however.

一目ぼれ can't be changed to １目ぼれ
一期一会 can't be changed to １期１会

not without a lot of head-scratching, anyway. 一人一人 would look funny as １人１人. But 一年生 and 1年生 are both fine.
Population of 四万人 is probably just as good as 40,000人, but a population of 42,325人 is far easier on the eyes than 四万二千三百二十五人.

So there is no "one size fits all" rule, other than make it as comprehensible to the reader as possible. The more technical the work, the better off you are using Arabic numerals, I think.

Sorry, it seems to be a lot of words dressed up as advice, without really answering your question. Hopefully some of it is useful.

Some more thoughts on this.

一歩、一方、一員、一説、一節、all seem to me to be Japanese expressions/phrases that do not lend themselves to represented by a mix of Arabic and kanji. In other words, keep them in kanji as you would 一目ぼれ.

一部、一番、第一、all feel fine expressed in kanji, and indeed might be weird if expressed as a mix of Arabic and kanji. I mean, if the expression is 一部の人が・・・ then yes I would definitely keep it as kanji. However, if the source text is talking about multiple, serial units of something, then it might make better sense to use as Arabic + kanji. 1番、2番、３番・・・415番 etc... is fine depending if the context calls for it.

一度 is something that might depend on the context. Is this a measurement of celcius/farenheit or a mesure of an angle? If so, Arabic numerals might be better. Or, is it expressing a "single time"? If so, that would be better off as a kanji phrase.

一つ、二つ、三つ etc... feels entirely viable in a horizontal context, but Arabic numerals also work.

I wonder if there is a better way to explain it without running on...

This was so helpful, thanks!

Majestic said:

Some more thoughts on this.

一歩、一方、一員、一説、一節、all seem to me to be Japanese expressions/phrases that do not lend themselves to represented by a mix of Arabic and kanji. In other words, keep them in kanji as you would 一目ぼれ.

一部、一番、第一、all feel fine expressed in kanji, and indeed might be weird if expressed as a mix of Arabic and kanji. I mean, if the expression is 一部の人が・・・ then yes I would definitely keep it as kanji. However, if the source text is talking about multiple, serial units of something, then it might make better sense to use as Arabic + kanji. 1番、2番、３番・・・415番 etc... is fine depending if the context calls for it.

一度 is something that might depend on the context. Is this a measurement of celcius/farenheit or a mesure of an angle? If so, Arabic numerals might be better. Or, is it expressing a "single time"? If so, that would be better off as a kanji phrase.

一つ、二つ、三つ etc... feels entirely viable in a horizontal context, but Arabic numerals also work.

I wonder if there is a better way to explain it without running on...

Click to expand...

As a possible simpler explanation, it sounds very similar to the guidelines that proofreaders of English follow when checking the use of numerals/words in text, i.e., you wouldn't say "love at 1st sight" or "When 1 is tired of London, 1 is tired of life." in standard writing but you would definitely give a population as a number. I think a good guideline is to do in Japanese what you would in English.

算用数字：0123456789

漢数字：零一二三四五六七八九十

大字（旧字体）：零壱弐参旨肆伍陸漆捌玖拾

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