Japanese Large Numbers: Man, Oku and Chō Beyond Ten Thousand

The core idea: a new unit word every four digits

An English speaker reads 123,456,789 in three-digit blocks, and the commas show where million and thousand go. A Japanese speaker reads the same digits in four-digit blocks. Counting from the right, the first four digits are an ordinary number, the next four are followed by man (万), and the next four by oku (億). So the number splits as 1 | 2345 | 6789 and is read ichioku nisen sanbyaku yonjūgoman rokusen nanahyaku hachijūkyū.

In the diagram the digits are identical; only the dividing lines move. That is the whole difficulty, and the whole solution. Once you can place the four-digit lines, you never need a word for hundred thousand, million or ten million, because each is just a number in front of man.

UnihongoVocabulary

一いち万まんの一いち万まん倍ばいが一いち億おくです。Ten thousand times ten thousand is one hundred million.

Converting in both directions, step by step

You need two procedures, one for reading printed digits aloud and one for writing down a figure you hear. If the numbers up to ichiman still feel slow, the beginner guide to numbers and counters covers that range; this article assumes it.

• Reading digits: count four digits from the right and draw a line; that line is man. Count four more and draw another; that is oku. Four more gives chō.
• Read each block as a normal number from 1 to 9999, then add its unit word. Skip empty blocks completely: 100,000,500 is 1億0000万0500, read ichioku gohyaku.
• Writing what you hear: give each unit its own four-digit block and pad with zeros. San'oku gojūman becomes 3 | 0050 | 0000, which is 300,500,000.
• Converting from English: a million is 100万, a billion is 10億, a trillion is 1兆. Learn these three anchors and work out the rest from them.

Japanese speakers do the same when a long number surprises them: they tap the digits from the right and recite the places under their breath, ichi, jū, hyaku, sen, man, jūman, and so on. Doing this in front of people is perfectly normal.

The conversion ladder: million, billion, trillion

The ladder below lists every step from ichiman to itchō. The pink rows are where Japanese introduces a new unit word, every fourth step; the blue tags mark where English does, every third step. Between the pink rows, Japanese simply counts up: ichiman, jūman, hyakuman, issenman.

Notice the bottom row. Twelve is divisible by both three and four, so at a trillion the two systems meet again, and one chō is exactly one trillion. It is the only place on the everyday ladder where a single English word matches a single Japanese one.

UnihongoVocabulary

一いち万まんの一いち万まん倍ばいが一いち億おくです。Ten thousand times ten thousand is one hundred million.

Sound changes: issenman, happyakuman and itchō

The sound changes follow the same logic as in smaller numbers. Hyaku, sen and chō begin with sounds that change after certain numbers, so hachi plus hyaku becomes happyaku, san plus sen becomes sanzen and ichi plus chō becomes itchō. Man and oku never change, because m and a vowel do not merge with anything: ichiman, hachiman, ichioku, hachioku, jūoku.

Sen on its own is a thousand, but ten million is usually said issenman, with the ichi kept, which is clearer when a lot of money is involved; plain senman is also heard. Happyakuman has a famous cousin: yaoyorozu no kami, written 八百万の神, literally the eight million gods, is the traditional way of saying that Japan has countless deities.

A used-car dealer and a customer are talking prices, and every figure crosses the man line.

Reading real figures: prices, salaries and populations

Printed Japanese usually writes digits for each block and kanji for the unit words: 1億2000万, sometimes 1億2千万. This is a gift to the learner, because the kanji show exactly where the four-digit lines fall. Estate agents often add a Western comma inside the man block, so a flat may be listed at 3,480万円. That comma sits inside the block and changes nothing: read sanzen yonhyaku hachijūman-en.

Salaries are given as a monthly figure, gekkyū, or an annual one, nenshū, and both are almost always in man. A news reader, an estate agent, a job applicant and two friends provide the scenes below.

Beyond the basics: rough numbers, keta and financial tables

Real conversation is full of approximate figures. Sū, several, goes in front of a unit: sūman-nin is tens of thousands of people, sūhyakuman-en is several million yen, sūsen'oku is hundreds of billions. Nan, how many, does the same job with a note of surprise: nan-oku-en mo is hundreds of millions of yen, said with raised eyebrows. Keta (桁) means a digit place, and keta ga chigau, literally the number of digits is different, means that two things are on completely different scales.

Business documents add one more trap. Financial statements and slides often print a unit note such as 単位：千円 or 単位：百万円, meaning all figures are in thousands or millions of yen. A cell showing 12,345 in a table marked 百万円 is 123億4500万円, hyakunijūsan'oku yonsen gohyakuman-en. Read the unit note first, then convert. Above chō there is kei (京), ten thousand chō, which you will meet mainly in science news.

How people say big numbers aloud

In conversation, en is often dropped once the topic is clear: a friend who has just bought a car says sanbyakuman shita, it cost three million. Ichiman on its own often means a ten-thousand-yen note: ichiman kuzushite moraemasu ka asks for change for one. Staff, by contrast, keep the full form and add polite endings, and on the phone they usually repeat large figures back with the unit to confirm them.

When accuracy matters, an agent will often write the price down or turn a calculator round to show you, and asking for that is polite and normal. A bank clerk is confirming a transfer.

Catching prices at the till at full speed is a separate listening skill with its own drill; here the aim is building and checking the big figures.

Common mistakes with man and oku

Saying jūni-sen for 12,000 is the classic first error. The printed comma sits after the thousands and invites a word-for-word twelve thousand. Japanese says ichiman nisen. Find the man line before you speak.

Saying senman for a million multiplies it by ten, because senman is ten million. The cause is the English idea of a thousand thousands. Anchor it as a hundred man: hyakuman.

Translating a billion as ichioku is the same error one level up. Oku feels like the next big word, but it is only a hundred million. A billion is jūoku.

Saying man-en for ten thousand yen comes from the fact that hyaku and sen can stand alone. Man never can: it is always ichiman. The same goes for ichioku and itchō.

Saying ichichō or hachichō happens when learners read the kanji one by one. The small pause belongs there: itchō, hatchō, and jutchō for ten trillion. Oku, by contrast, never changes, so hachioku and jūoku stay as they are.