How to Say Math Stuff in Japanese

We have enjoyed a fairly mild December in Japan so far this year. However, starting today, the temperature will finally become 一桁（ひとけた）. The 桁 refers to columns or beams; in this case, it indicates the one’s column for numbers, which is a roundabout way of saying that the temperature will be under 10°C starting today. Brrr!

All this talk of cold temperatures reminds me that I don’t know how to do division. I mean, of course I can do division itself, even “long division.” Why do they teach us long division anyway? Why not “short division” so we can get the misery over sooner? But my point is that I did not yet learn how to say mathematical division statements out loud in Japanese.

That changed as of today, when I asked my resident native Japanese speaker for help. After reminding me that she hasn’t had to calculate square roots since high school, she provided the following translations for basic math features, the kind you might perform on a simple calculator (電卓（でんたく）).

Addition and Subtraction

The verb 足（た）す, without conjugation, is used to add numbers together. For subtraction, use 引（ひ）く, the same verb used to pull on a door handle.

• 1 + 2 = 3: 一（いち）足（た）す二（に）は三（さん）です。
• 3 – 2 = 1: 三（さん）引（ひ）く二（に）は一（いち）です。

Multiplication and Division

Multiplication uses the verb 掛（か）ける, although it is typically written using kana instead of kanji. Use the verb 割（わ）る when dividing numbers.

• 2 × 3 = 6: 二（に）かける三（さん）は六（ろく）です。
• 6 ÷ 3 = 2: 六（ろく）割（わ）る三（さん）は二（に）です。

Squares and Square Roots

If you search for “square root” in your English-Japanese dictionary, a whole bunch of complicated words show up. However, I’ve been assured that ルート is correct for mundane calculations. To take the square of a number, add の followed by 二乗（じじょう）.

• √9 = 3: ルート九（きゅう）は三（さん）です。
• 3² = 9: 三（さん） の二乗（じじょう）は九（きゅう）です。

Decimals, Fractions, and Negatives

When speaking decimals, use 点（てん） for the decimal point.

• 25.03: 二（に）十（じゅう）五（ご）点（てん）ゼロ三（さん）

Fractions appear reversed from their spoken English forms; mention the denominator first. The phrase 分（ぶん）の goes between the two fraction terms. Whole numbers paired with the fraction appear first, followed by と.

• 2/3: 三（さん）分（ぶん）の二（に）
• 1-2/3 (that is, “one and two-thirds”): 一（いち）と三（さん）分（ぶん）の二（に）

Negative numbers are the easiest of all. Simply start them with the English-derived word マイナス.

• -34: マイナス三（さん）十（じゅう）四（よん）

That should get you through basic calculator arithmetic. Now if you’ll excuse me, I really need to find somewhere warm to get away from these frigid 一桁 temps.

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