11–99 | Chinese (Mandarin) Grammar

Here is the moment Chinese numbers pay off for English speakers. English forces you to memorise a pile of special words — "eleven, twelve, thirteen" and then "twenty, thirty, forty" — none of which transparently means what it counts. Chinese has none of that. Every number from 11 to 99 is built by literal arithmetic on the digits you already learned on the 0–10 page: 二十一 is spelled out "two-ten-one" and equals 2×10+1 = 21. Learn the single composition rule below and you can say every two-digit number instantly, with nothing left to memorise.

The composition rule

The pattern is: (tens digit) + 十 + (ones digit), where each slot is optional at the ends.

11–19 — no tens digit is spoken; start straight from 十: 十一 (shíyī) 11, 十二 (shí'èr) 12, … 十九 (shíjiǔ) 19.
20, 30, … 90 — tens digit + 十, no ones: 二十 (èrshí) 20, 三十 (sānshí) 30, … 九十 (jiǔshí) 90.
The rest — all three slots filled: 二十一 (èrshíyī) 21, 四十五 (sìshíwǔ) 45, 九十九 (jiǔshíjiǔ) 99.

Number	Characters	Pinyin	Literally
11	十一	shíyī	ten-one
12	十二	shí'èr	ten-two
15	十五	shíwǔ	ten-five
19	十九	shíjiǔ	ten-nine
20	二十	èrshí	two-ten
21	二十一	èrshíyī	two-ten-one
34	三十四	sānshísì	three-ten-four
58	五十八	wǔshíbā	five-ten-eight
99	九十九	jiǔshíjiǔ	nine-ten-nine

我今年二十五岁。

wǒ jīnnián èrshíwǔ suì.

I'm twenty-five this year. (neutral) — 二十五 = 'two-ten-five'.

这个班有三十八个学生。

zhège bān yǒu sānshíbā ge xuésheng.

This class has thirty-eight students. (neutral)

他爷爷已经九十九岁了。

tā yéye yǐjīng jiǔshíjiǔ suì le.

His grandfather is already ninety-nine. (informal) — the top of the two-digit range.

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The whole system after ten is arithmetic. 二十一 is literally 2×10+1; 五十八 is 5×10+8. There are no teen-words and no -ty forms hiding surprises — once 一 through 十 are solid, you can already produce every number to 99 without learning anything new.

Why 11 is 十一, not 一十一

At the very start of a number, the tens digit "1" is left unspoken: 11 is 十一, not 一十一; 15 is 十五. You only add a leading 一 to "ten" when the ten sits inside a bigger number — 一百一十 (yìbǎi yīshí) 110 — territory for the hundreds and thousands page. For everyday counting from 11 to 19, the rule is simply: begin with 十.

(You will occasionally meet 一十一 in formal, legal, or accounting contexts where every place is spelled out to prevent tampering — but in ordinary speech and writing it sounds wrong. Say 十一.)

一共十二个人来了。

yígòng shí'èr ge rén lái le.

Twelve people came in total. (neutral) — 十二, not 一十二.

The 十 in the middle is not optional

The mirror-image mistake is dropping 十 from the tens. 25 is 二十五 (two-ten-five); the 十 is what makes it "twenty-five" rather than the two separate digits "2, 5." Without 十 you have said 二五 (èr wǔ), which is read as a pair of digits (as in a bus route or a code), not the quantity twenty-five.

从这儿到机场大概二十分钟。

cóng zhèr dào jīchǎng dàgài èrshí fēnzhōng.

It's about twenty minutes from here to the airport. (informal) — 二十, with the 十.

现在是九点四十五。

xiànzài shì jiǔ diǎn sìshíwǔ.

It's nine forty-five. (neutral) — 四十五 keeps its 十.

Two is 二 inside these numbers — never 两

On the 0–10 page you met the split between 二 (èr) and 两 (liǎng) for "two." Two-digit numbers make the rule sharp: inside a compound number, the digit two is always 二 — 二十 (20), 十二 (12), 二十二 (22). You never say 两十 for twenty.

The subtle part: this holds even when the number sits right before a measure word. "Twenty-two people" is 二十二个人 — the ones-place two stays 二, because it is part of the number 二十二, not a standalone "two." The special form 两 replaces only a bare, standalone two before a classifier (两个人, 两杯水); it never touches the ones digit of a larger number.

二十二个箱子都搬上来了。

èrshí'èr ge xiāngzi dōu bān shànglái le.

All twenty-two boxes have been carried up. (neutral) — 二十二个, not 二十两个.

请翻到第三十二页。

qǐng fān dào dì sānshí'èr yè.

Please turn to page thirty-two. (neutral) — 三十二, with medial 二.

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Two rules, one slogan. Inside any compound number, two is 二: 二十, 十二, 二十二 — even before a measure word (二十二个人). The form 两 appears only for a lone "two" that directly quantifies (两个, 两百). Full details on the 两 vs 二 page.

A pronunciation footnote: 十二 and any medial 二 need a pinyin apostrophe to mark the syllable boundary — shí'èr (12), èrshí'èr (22), sānshí'èr (32) — because a vowel-initial syllable following another syllable would otherwise be ambiguous. The apostrophe is purely a spelling aid; nothing changes in the sound.

Numbers before nouns

A two-digit number behaves like any number: put it in front of a measure word and then the noun. The number itself doesn't change shape when it quantifies.

这本书才十五块钱。

zhè běn shū cái shíwǔ kuài qián.

This book is only fifteen yuan. (informal) — 十五 + 块.

打折以后只要六十六块。

dǎzhé yǐhòu zhǐ yào liùshíliù kuài.

After the discount it's only sixty-six yuan. (informal)

Common Mistakes

1. Adding a leading 一 to the teens. At the start of a number, "ten-something" begins with bare 十.

❌ 一十一

Wrong (in ordinary use) — 11 is 十一; a leading 一 belongs only inside larger numbers.

✅ 十一

shíyī

eleven

2. Dropping 十 from the tens. Without 十 you've written two separate digits, not a two-digit number.

❌ 二五

Wrong for '25' — 二五 reads as the two separate digits '2, 5'; twenty-five must include the tens word: 二十五.

✅ 二十五

èrshíwǔ

twenty-five

3. Using 两 inside a compound number. The digit two is 二 in 二十, 十二, and the ones place of 二十二 — even before a measure word.

❌ 二十两个人

Wrong — the ones-place two stays 二: 二十二个人.

✅ 二十二个人

èrshí'èr ge rén.

twenty-two people

4. Reading 二十 as if it were two separate digits. 二十 is "two-ten" = 20; the digit string "2, 0" (a label like a year or bus number) is 二〇.

❌ 我有二〇个苹果。

Wrong — the quantity twenty is 二十, not the digit string 二〇.

✅ 我有二十个苹果。

wǒ yǒu èrshí ge píngguǒ.

I have twenty apples.

Key Takeaways

The rule is (tens digit) + 十 + (ones digit), utterly regular from 11 to 99.
11–19 start with bare 十 (十一, not 一十一); 20–90 are digit + 十 (二十, 三十).
The medial 十 is mandatory — 二十五, never 二五 — or you've written separate digits.
Inside a compound, two is always 二 (二十, 十二, 二十二), even before a measure word; 两 is only for a standalone two (两个).
Medial 二 takes a pinyin apostrophe: shí'èr, èrshí'èr — a spelling aid only.
Once 1–10 are solid, you already know every number to 99.

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