Numbers 11–99

Here is the good news that English speakers rarely expect: once you know the Sino numbers 一 through 十 and the word 十 (jū, "ten"), you already know every number from 11 to 99. There is nothing new to memorize. Japanese builds two-digit numbers by pure place-value logic — literally "ten-one," "two-ten," "two-ten-three" — with zero irregular forms. No "eleven," no "twelve," no "twenty" that hides the "two." It is arguably the most reassuring corner of Japanese grammar, and this page shows you the mechanism so you can generate any number on demand.

The building blocks

Everything in this range is assembled from the Sino digits 1–9 plus 十. Here they are as a reminder:

If these aren't solid yet, drill them first on Sino Numbers 1–10, because the whole system below is just those ten characters recombined.

The teens: 十 + digit (11–19)

To make eleven through nineteen, write 十 first, then the units digit. That's it. 十一 is "ten-one" = 11, 十五 is "ten-five" = 15. There is no separate word for the teens the way English has "-teen."

The tens: digit + 十 (20, 30, 40…)

To make the round tens, reverse the order: put the multiplier digit first, then 十. 二十 is "two-ten" = 20, 三十 is "three-ten" = 30. The position of the digit relative to 十 is what tells you whether you're multiplying or adding — a digit before 十 multiplies it, a digit after 十 adds to it.

Reassuringly, 十 stays jū in every one of these — the tens themselves trigger no sound changes. (The euphonic shifts you may have heard about — sanbyaku, roppyaku — only kick in at the hundreds and above; see Sound Changes in Numbers.)

Putting it together: two-digit numbers (21–99)

Now combine both moves. A number like 47 is "four-ten" (the tens block) followed by "seven" (the units): 四十七. Read strictly left to right, big place to small place, and it spells itself out: yon-jū-nana.

Why 4, 7, and 9 have two readings — and which to pick

The digits 四 (4), 七 (7), and 九 (9) each have two readings, and in compound numbers there is a strong default:

• 四 → prefer よん (yon), not shi. (Shi is homophonous with 死 "death" and is avoided.)
• 七 → prefer なな (nana), not shichi. (Shichi is easily misheard as ichi.)
• 九 → prefer きゅう (kyū), not ku. (Ku is homophonous with 苦 "suffering.")

So 47 is よんじゅうなな yon-jū-nana, not shi-jū-shichi. These native-derived readings (yon, nana) dominate in counting because they're clearer and dodge the unlucky homophones. You will still hear shi and shichi in fixed contexts (telling time, some set phrases), but for building numbers, default to yon, nana, kyū.

The big picture: everything is buildable

Step back and notice what you now have. English forces you to memorize twenty-eight separate number-words before you reach a fully regular pattern ("twenty-one, twenty-two…"). Japanese asks you to memorize just eleven (1–10 and the word for ten), after which every number up to 99 is generated by a single rule: multiplier before 十, addend after 十. And the very same logic scales upward — swap in 百 (hundred), 千 (thousand), 万 (ten-thousand) and you can build any number at all. That compositional transparency, covered next on Hundreds, Thousands, and 万, is one of the genuine gifts of the Japanese counting system.

Common mistakes

English speakers who over-apply the "digit + 十" pattern sometimes write 一十 for 10, by analogy with 二十, 三十. But 十 stands alone: there is no 一 in front. (The single exception is far up in the large numbers — 一千, 一万 — where the leading 一 is required; that's a separate rule covered later.)

Reading 47 as shi-jū-shichi is grammatically parseable but sounds unnatural and risks being misheard. Native counting uses yon-jū-nana.

十 is jū with a long vowel — two full beats (じゅ・う). Clipping it to ju (one beat) is a common and audible pronunciation slip.

Order is everything. 十五 (ten-five = 15) and 五十 (five-ten = 50) use the same two characters in opposite order and mean completely different numbers. A digit before 十 multiplies; after 十 it adds.

Key takeaways

• Teens (11–19): 十 + digit — 十一 (11), 十五 (15), 十九 (19). No "-teen" irregularity.
• Tens (20–90): digit + 十 — 二十 (20), 三十 (30), 九十 (90). Never 一十 for 10.
• Two-digit numbers: tens block + units — 四十七 (yon-jū-nana), read big-place to small-place.
• Prefer よん (4), なな (7), きゅう (9) in counting to avoid unlucky homophones and mishearing.
• 十 stays jū throughout this range; sound changes (sanbyaku, roppyaku) only start at the hundreds.