Japanese Numbers and Dates

Big numbers are where careful translators slow down. Japanese groups digits differently from English, and a moment of autopilot turns ten thousand into a hundred thousand.

Grouping by ten thousand

English groups large numbers in threes: thousand, million, billion. Japanese groups in fours, around the unit 万 (man), which is ten thousand. After that, 億 (oku) is a hundred million and 兆 (chō) is a trillion.

So a price of 30,000 yen is written 三万円 (san-man en), literally "three man yen". The trap is reading 万 as "thousand". 三万 is thirty thousand, not three thousand. A whole population or budget can be off by a factor of ten if you slip here.

Counting that changes the word

Numbers attach to counter words that depend on what you are counting, and the number itself can change shape. One person is 一人 (hitori), not "ichi-nin". Two is 二人 (futari). This is its own topic, covered in the counters guide, but it is worth knowing that "two" is rarely just "two".

Era years

Alongside the Western calendar, Japan counts years by imperial era. Official forms, news, and coins often use it, so you cannot ignore it.

To convert, add the era's start year and subtract one. Reiwa 6 is 2019 plus 6 minus 1, which is 2024. A document dated 令和6年 is from 2024, and a tool that leaves it as "Reiwa 6" has not actually finished the job.

Date order

Japanese writes dates largest unit first: year, then month, then day. 2024年3月5日 is the 5th of March, 2024. This order is unambiguous, which is more than can be said for the English habit of writing 3/5 and leaving the reader to guess month or day.