Numbers & Counting

Numbers in Japanese have two surprising properties that trip up new learners. First: they group at ten thousand, not at thousand, so converting big numbers to and from English requires arithmetic. Second: you can't just say "two cats" — you need a counter word that depends on what you're counting. This guide walks through both.

0 through 10

Like most languages, Japanese has special words for the digits. A few of them have two readings — pick whichever feels more natural in context (some compounds prefer one, some the other).

The duplicates are partly historical, partly practical. Four (shi) sounds identical to "death" (死), so yon is preferred in many contexts — counting people, for instance. Seven and nine have similar superstition-driven alternates. You'll absorb which is used where through repetition.

11 through 99

Built compositionally. Eleven is "ten one" (十一, jūichi). Twenty is "two ten" (二十, nijū). Twenty-three is "two ten three" (二十三, nijūsan). The pattern is rigorously predictable.

100, 1,000, and the great divide at 10,000

One hundred is 百 (hyaku); one thousand is 千 (sen). Both compose like English: 200 is "two hundred" (二百, nihyaku); 5,000 is "five thousand" (五千, gosen).

And then comes the major break. Japanese groups numbers by ten thousands, not thousands. The dividing word is 万 (man). 10,000 is "one man." 100,000 is "ten man." 1,000,000 is "one hundred man." This is where converting between languages becomes a real exercise.

The pattern repeats: after 万 (10⁴) comes 億 (10⁸, "oku") and 兆 (10¹², "chō"). Each is 10,000 times the last. This is why a Japanese person reading "1,000,000 yen" mentally regroups it to "百万 (hundred-thousand)" — they're translating from your grouping to theirs.

Counters: you can't just count things

Here's the part that surprises everyone. In Japanese, you don't say "two cats" — you say "two-counter cats," where the counter changes depending on what kind of thing you're counting. This is similar to how English says "two sheets of paper" or "two head of cattle" — except Japanese does it essentially every time. There are over 500 counters in existence. You only need about 10 to function.

The big ones

The reading shifts (rendaku)

Counters often have small phonetic adjustments depending on the number that comes before them. Look at 本 above — "one bottle" is ippon, "two bottles" is nihon, "three" is sanbon. The h shifts to p/b in a pattern that's regular per counter but doesn't generalize across counters.

The counter 人 ("people") is exceptional: 1 = ひとり (hitori), 2 = ふたり (futari), 3+ = sannin and onward by the regular pattern. So "one person" and "two people" use kun-style readings; everything else switches to on.

The traditional counting system (one through ten)

For small numbers of unspecified things — when you don't know or don't care about the right counter — Japanese has an older, generic counting set: hitotsu, futatsu, mittsu, yottsu, itsutsu... They're a fallback you can use without knowing the proper counter. They top out at ten (tō); past that, you're forced to pick a counter.

This is genuinely useful as a beginner. When you can't remember what counter to use for, say, candy or a piece of fruit, you can fall back to 三つ ("three of them") and be understood without sounding wrong.

Saying the time

Quick bonus: the time uses two specific counters, 時 (ji, hour) and 分 (fun / pun, minute). Three o'clock is 三時 (san-ji); 3:15 is 三時十五分 (san-ji jūgo-fun). Like other counters, the minute one has phonetic shifts: 1 minute is ip-pun, 3 minutes is san-pun, 10 is jup-pun. Pattern, not chaos.