Do you know your math in Japanese?

Do you know your math in Japanese?

Without knowing the relevant vocabulary, your 数学 (sūgaku, math) ability will be next to nothing when studying or working in Japanese!

When I spent time in school, I found maths lessons to be the easiest to follow, because visually it looks so similar. But what if you have to read your workings aloud? Let’s go over some of the basic symbols and principles to get you to the level of a Japanese lower school child!

Bonus

Download a free cheatsheet that will help you master math in Japanese.

The first thing that you’re going to need to know are Japanese numbers. In day to day school working Japanese children use Arabic numerals as we would use (1, 2, 3, etc.) but numbers in their kanji form do appear.

Japan uses international mathematical conventions when transcribing algebra on paper, so the only issue comes when you have to read your working out aloud. Let’s take a look!

You’ll need to be familiar with:

  • です copula
  • なる verb
  • して下さい request
  • か question particle
  • の possessive particle
  • に direction particle
  • から origin particle

The most important thing to remember when doing maths is the use of the copula です. です states exactly what something equals when used with は; in English we use the verb ‘to be’ for both existence and demonstrating equality (as a predicate). In Japanese, we just use です as Japanese has other existential verbs (such as ある and いる). So 「ωは50です。」means that ω has a value of 50. ω and 50 are equal.

N.B. It’s also necessary that you as a bare minimum are able to read hiragana and katakana in order to understand this post. Moreover, I’ve occasionally used です to demonstrate the function grammatically, but in the real world you’d rarely say です when speaking sums out aloud.

. Decimal numbers

Firstly, notice that we say 点 (てん) to read aloud the decimal point. The kanji 点 literally means ‘point,’ used even when speaking about an abstract, “I’d like to make a point...” kind of point.

3.5 さんてんご 190.2 ひゃくきゅうじゅうてんに

A note about Japanese pronunciation: Due to the rules that all Japanese follow regarding using four morae, you’ll often find that in certain cases, you’ll need to either leave a pause with the use of っ or extend the last vowel sound. 1.2 would become いってんに rather than いちてんに as you may otherwise expect.

Likewise, you may feel that you need to extend the vowel sound at the end of some numbers to make your Japanese flow better, such as 2.5 becoming にーてんご rather than にてんご, as would first appear. There are no hard and fast rules, it’s all about practice and experience—and generally what’s easiest to say is how it’s said in Japanese!

+ Addition

Although the + sign is used, the verb 足す (たす, to add, to top up) is used when describing sums of addition.

7 + 3 = 10 七足す三は十です。 ななたすさんはじゅうです。

Add 100 to 200 and it becomes 300. 百と二百を足すと三百になる。 ひゃくとにひゃくをたすとさんびゃくになる。

Please add 5 to 2.5 2.5に5を足して下さい。 にてんごにごをたしてください。

We can see therefore that standard grammatical patterns are followed when using this verb. It’s no surprise that in addition to the native Japanese word, an imported word has made its way into the every day vocabulary, in the form of the word ‘プラス’, which of course means plus.

7 + 1 = 8 七プラスいちは八です。 ななプラスいちははちです。

Subtraction

Just as we have the Japanese word プラス written in a katakana script, we also have the opposite, which is マイナス. It’s used exactly as you’d expect:

100 - 40 = 60 百マイナス四十は六十です。 100 minus 40 is 60.

7,000 - 300 = ? 七千マイナス三百はなんなんですか? What’s 7,000 minus 300?

Of course, there is a native Japanese verb that we can use.

を引いて

−4から−7を引くと,+3 If you take −7 from −4, you end up with +3.
(notice the use of から here to denote ‘from’)

Japanese numbers and counting

× Multiplication

We use the verb 掛ける [かける], which can mean a multitude of things, but for our purposes, means ‘multiply’.

70 x 3 = 280
七十掛ける三は二百十八です。 ななじゅうかけるさんはにひゃくじゅうはちです。

5 x 3 =15
3に5を掛けると15になる。 If you multiply 5 by three, it becomes 15.
(note the use of the に particle here to show direction)

÷ Division

We use the verb 割る[わる - to divide] when speaking about mathematical divisions (for literal ones we use分ける[わける]. It follows every pattern of the examples that we have looked at above.

10 ÷ 5 = 2
十割る五は二です。

Is the tangent cosine divided by sine?
タンジェントってサインでコサインを割る?

Fractions

Fractions are conveyed by using the kanji 分[ぶん]meaning 'part''. You need to conceptualise fractions in a different way when thinking in Japanese, as we use the possessive particle の to indicate that of the whole (the denominator), there is a part about which we are speaking (numerator). So, it's not one third (that is to say one part of a whole which is a third of the value), it's third's one (that is to say it’s one part of three parts).

1/3 三分の一 さんぶんのいち

2/5 五分の二 ごぶんのに

How was that little maths lesson for you? Do you know of any other ways in which you can express mathematical functions in Japanese? If so, let me know in the comments! And if you're particularly passionate about maths, be sure to consider the advanced Japanese dictionary of mathematics.

Oh, and as an extra treat, check out this awesome video which explains a method of multiplying long numbers that you may have never known of before:

Click below to download the free Japanese math cheatsheet:

Japanese math cheatsheet