Found a sentence,


Is this how you write ratios in Japanese?

  • 5
    I think 1:7 is 1対7. 7分の1 is 1/7. – Yang Muye Jul 13 '15 at 14:13

Not exactly (as several have commented). This is how you talk about fractions in Japanese:

7分の1 → 1/7

Literally, you can think about it as 'one part of seven'. It is not a ratio, i.e. 'one part to seven parts', as that equates to 1/8.

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  • This is correct. Ratio is 1:7, and fraction is 1/7 in Japanese language (not mathematics). – CookieMonster Jul 15 '15 at 12:03

Yes, 「7分の1」 means same as 1:7 mathematically.

1:7 = (1/8):(7/8) = (1/8)/(7/8) = (1/8)x(8/7) = 8/56 = 1/7

However, in Japan, kids are taught that 1:7 is 「[比]{ひ}」 and 1/7 is 「[分数]{ぶんすう}」. I guess that 「比」 is translated as "ratios", and 「分数」 is translated as "fractions" generally. So, Japanese people tend to think that 1/7 is not a ratio, maybe.

In English, both 1:7 and 1/7 can be read "one to seven", right? And both 1:7 and 1/7 are called "ratio" in some cases, maybe? (Sorry, if my knowledge about English is wrong.) But in Japanese, each of them has its own way to be read.

1:7 is read 「[1]{いち}[対]{たい}[7]{なな}」.


1/7 is read 「[7]{なな}[分]{ぶん}の[1]{いち}」.

There are other ways to express proportions in Japanese. For example,

1/10 is read 「[1]{いち}[割]{わり}」 = 10%

2/10 is read 「[2]{に}[割]{わり}」 = 20%

Which word should be used is up to the situation and context.

If your "ratio" means both 1:7 and 1/7, I would answer that there are several ways to write ratio in Japanese, and 「7分の1」 is one of them. So, yes.

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n / m = n : m

is written


where "m" and "n" are positive integers.

BTW, is


more acceptable for you?

* added *

I just learned that the notation n : m confuses some people.

Here is what Hans Lundmark pointed out to me in regard of the usage of n : m. I hope this helps to resolve their confusion.

You have good historical reasons for interpreting n:m as n/m.

From http://jeff560.tripod.com/operation.html:

The colon (:) was used in 1633 in a text entitled Johnson Arithmetik; In two Bookes (2nd ed.: London, 1633). However Johnson only used the symbol to indicate fractions (for example three-fourths was written 3:4); he did not use the symbol for division "dissociated from the idea of a fraction" (Cajori vol. 1, page 276).

Gottfried Wilhelm Leibniz (1646-1716) used : for both ratio and division in 1684 in the Acta eruditorum (Cajori vol. 1, page 295).

As for the said excerpt, it reads "The (average?) physical ability of humankind is one-seventh of that of vampire."

* added (again) *

In view of the established usage as described in http://www.bradford.ac.uk/wimba-files/msu-course/media/ratio%20teaching%20new.pdf , the assertion by @Earthliŋ

n : m is usually the notation for "n parts in (n+m) parts vs. m parts in (n+m) parts", so 1:7 would correspond to 1/8 and 7/8

should read

In the context that something is to be divided into n : m, it can be considered as "n parts in (n+m) parts vs. m parts in (n+m) parts", so 1:7 can be specified as the pair (1/8, 7/8) if needed.

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  • 5
    No! n : m is usually the notation for "n parts in (n+m) parts vs. m parts in (n+m) parts", so 1:7 would correspond to 1/8 and 7/8. – Earthliŋ Jul 13 '15 at 15:44
  • @ Earthliŋ: Aren't you confusing part-to-oat ratio with part-to-whole ratio? – eltonjohn Jul 14 '15 at 0:54
  • 2
    I don't think I am. Maybe the OP could clarify whether by 1:7 he meant 1/7. – Earthliŋ Jul 14 '15 at 1:02
  • @ Earthliŋ: You may want to have a look at this -> en.wikipedia.org/wiki/Ratio . – eltonjohn Jul 14 '15 at 1:40
  • @ Earthliŋ: And this, too, may be of help -> bradford.ac.uk/wimba-files/msu-course/media/… . – eltonjohn Jul 14 '15 at 2:16

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