Japanese uses two parallel sets of numbers from 1 to 10, a unique system for grouping large numbers by ten-thousands instead of thousands, and special “counter” words that change depending on what you’re counting. It sounds like a lot, but the core system is logical once you see how the pieces fit together.
The Two Number Systems: 1 to 10
Japanese has two ways to say every number from 1 to 10. The first is the Sino-Japanese (kango) system, borrowed from Chinese centuries ago. This is the set you’ll use most often and the one that extends to larger numbers. The second is the native Japanese (wago) system, which only covers 1 through 10 and shows up in specific situations like general counting, dates, and counting people.
Here are both sets side by side:
- 1: いち (ichi) / ひとつ (hitotsu) — 一
- 2: に (ni) / ふたつ (futatsu) — 二
- 3: さん (san) / みっつ (mittsu) — 三
- 4: し or よん (shi/yon) / よっつ (yottsu) — 四
- 5: ご (go) / いつつ (itsutsu) — 五
- 6: ろく (roku) / むっつ (muttsu) — 六
- 7: なな or しち (nana/shichi) / ななつ (nanatsu) — 七
- 8: はち (hachi) / やっつ (yattsu) — 八
- 9: きゅう (kyū) / ここのつ (kokonotsu) — 九
- 10: じゅう (jū) / とお (tō) — 十
Notice that 4 and 7 each have two Sino-Japanese readings. し (shi) sounds like the word for death, so よん (yon) is preferred in many everyday contexts. Similarly, なな (nana) is more common than しち (shichi) because shichi can be confused with いち (ichi) when spoken quickly.
For anything above 10, you’ll almost always use the Sino-Japanese system. The native Japanese counting words essentially stop at 10 in modern usage.
Building Numbers From 11 to 99
Once you know 1 through 10 in the Sino-Japanese system, larger numbers follow a simple formula. Japanese numbers are built by stacking the components together, saying exactly what the number is made of.
11 is じゅういち (jū-ichi), literally “ten-one.” 25 is にじゅうご (ni-jū-go), literally “two-ten-five.” 99 is きゅうじゅうきゅう (kyū-jū-kyū), “nine-ten-nine.” You always state the multiplier first, then the place value, then add the ones digit. There are no new words to memorize between 11 and 99.
Hundreds, Thousands, and Beyond
The pattern continues with 100, which is ひゃく (hyaku), and 1,000, which is せん (sen). So 300 is さんびゃく (sanbyaku), 5,000 is ごせん (gosen), and 4,562 is よんせんごひゃくろくじゅうに.
Here’s where Japanese diverges from English in a significant way. English groups large numbers by thousands: thousand, million, billion, trillion. Japanese groups by ten-thousands. The key unit is 万 (まん, man), which equals 10,000. So where English speakers think “one hundred thousand,” Japanese speakers think “ten man” (じゅうまん). One million is ひゃくまん (hyaku-man), literally “one hundred ten-thousands.”
The next major unit after 万 is 億 (おく, oku), which equals 100 million. After that comes 兆 (ちょう, chō), which equals one trillion. Written numerals in Japan still use commas every three digits, but speakers mentally chunk the number in groups of four. This mismatch trips up learners regularly, so when you see a large number written out, practice grouping the digits in fours from the right to find the Japanese reading.
Counters: Why You Can’t Just Say a Number
In English, you can say “three dogs” or “five books” by placing a number directly before the noun. Japanese requires a counter word between the number and the thing you’re counting, similar to how English uses “three sheets of paper” or “two slices of bread,” except Japanese does this for nearly everything.
The most important counter to learn first is つ (tsu), which uses the native Japanese numbers. It works as a general-purpose counter for almost any object when you don’t know the specific counter. みかんが３つあります means “there are three oranges.” This counter only works from 1 to 10, matching the native number set: ひとつ, ふたつ, みっつ, and so on.
Beyond つ, here are the counters you’ll encounter most often:
- 人 (にん, nin): Counts people. One person is ひとり (hitori) and two people is ふたり (futari), both using native Japanese readings. From three onward it switches to Sino-Japanese: さんにん, よにん, ごにん.
- 個 (こ, ko): Counts objects with a distinct shape or boundary, like apples, eggs, or boxes. Works for most small, compact items.
- 本 (ほん, hon): Counts long, cylindrical objects: pens, bottles, trees, rivers, phone calls, even movies.
- 枚 (まい, mai): Counts flat, thin objects: sheets of paper, plates, shirts, tickets.
- 匹 (ひき, hiki): Counts small to medium animals: cats, dogs, fish, insects.
There are hundreds of counters in Japanese, but these five plus the general つ counter will get you through the vast majority of daily situations.
Sound Changes When Combining Numbers and Counters
When certain numbers meet certain counter sounds, the pronunciation shifts. These changes follow consistent rules, so once you learn the pattern you can predict them.
The numbers 1 (いち), 6 (ろく), 8 (はち), and 10 (じゅう) are the main culprits. When these numbers appear before a counter that starts with k, s, t, or h sounds, the final syllable of the number gets clipped and the first sound of the counter doubles. For example, 1 plus 個 (ko) doesn’t become いちこ but いっこ (ikko). 8 plus 歳 (sai) becomes はっさい (hassai), not はちさい.
Counters starting with an h-sound get extra treatment. Before the numbers 1, 6, 8, and 10, the h changes to a p-sound. So 6 plus 本 (hon) becomes ろっぽん (roppon), and 10 plus 匹 (hiki) becomes じゅっぴき (juppiki). Before the number 3, the h changes to a b-sound instead. 3 plus 匹 (hiki) becomes さんびき (sanbiki), not さんひき.
These shifts exist because they make the words easier to say quickly. You’ll internalize them through practice faster than through memorization.
Counting Days of the Month
Days of the month use their own set of readings, and the first ten days are almost entirely irregular. These are among the most commonly used native Japanese number words, and they need to be memorized individually:
- 1st: ついたち (tsuitachi)
- 2nd: ふつか (futsuka)
- 3rd: みっか (mikka)
- 4th: よっか (yokka)
- 5th: いつか (itsuka)
- 6th: むいか (muika)
- 7th: なのか (nanoka)
- 8th: ようか (yōka)
- 9th: ここのか (kokonoka)
- 10th: とおか (tōka)
After the 10th, most dates switch to the regular Sino-Japanese number plus にち (nichi). So the 11th is じゅういちにち, the 15th is じゅうごにち, and so on. But a few more irregular readings lurk: the 14th is じゅうよっか (jūyokka), the 20th is はつか (hatsuka), and the 24th is にじゅうよっか (nijūyokka). Every other date from 11 through 31 follows the standard pattern.
A Practical Starting Point
If you’re just beginning, focus on the Sino-Japanese numbers 1 through 10 first. Practice combining them to form 11 through 99 until the stacking pattern feels automatic. Then memorize the native Japanese set (ひとつ through とお) so you can use the general つ counter. From there, add one or two specific counters at a time, starting with 人 for people and 個 for objects. The irregular day-of-the-month readings are worth drilling early too, since dates come up constantly in conversation and travel. Everything else, from large numbers to the hundreds of specialized counters, will layer on naturally as you encounter them.