CEDICT shows 兆 as "… / million / mega- / trillion / tera- / billion (old)".

Is it ever actually used numerically, or is it standard to use Arabic numbers (or M/T for prefixes) to eliminate ambiguity?

Speaking of ambiguity, an answer and a comment say it is more commonly used for million/mega, while another answer says trillion/tera is standard.

  • Mostly used for Mbps nowadays. Internet speeds are advertised like 100兆/200兆.
    – Mou某
    Commented Jan 24, 2018 at 5:01
  • 千赫 kHz, 兆赫 MHz usually written kHz,MHz
    – user6065
    Commented Jan 24, 2018 at 5:49
  • @user3306356: That would make it "mega" while Tang Ho seems to say it should only be used for "tera"
    – 伟思礼
    Commented Jan 24, 2018 at 6:52
  • see 3rd line of answer by mentioned user, also bkrs:兆 omen; million; mega; also trillion. China = million; Japan and Taiwan = trillion (bkrs: 2) миллион; мега- 兆赫 [zhàohè] физ. - мегагерц)
    – user6065
    Commented Jan 24, 2018 at 7:28
  • @伟思礼 tera should be 太.
    – Mou某
    Commented Jan 24, 2018 at 7:35

5 Answers 5


Outside the IT world, 1兆 is 10^12, or 1万 x 1亿. But you won't see this use very much now.

Inside the IT world, (when you talk about the size of hard disk, memory, etc ...) 1兆 is 1M, which is 1024k, approximately 10^6. The might be the more common use nowadays.


When used in SI unit, 兆 mean 10^6 in mainland China and 10^12 in Taiwan. The use in IT world actually comes from this usage, with an altered value. It is actually part of the unit, not the number.

  • According to Chinese (mainland) national standard, 10^6 in SI units should be 兆, and 10^12 should always be 万亿, never 兆. zjj.beijing.gov.cn/wsbs/infoview.asp?ViewID=50494 10的4次方称为万,10的8次方称为亿,10的12次方称为万亿
    – Victor
    Commented Nov 28, 2019 at 11:52

In the decimal system we have

一 10^0, 十 10^1, 百 10^2, 千 10^3, 万 10^4

Remember, the power indicates the quantity of zero appears behind a single number.

We array these units when reading a big number, as 万千百十个 (where 个/个位 means single digit or the unit). For example, 96,128 is reading as 九万六千一百二十八.

A number which is bigger than (or equal to) 10^5, will be presented circularly by these units as 千百十万千百十个. For example, 75,896,128 is reading as 七千五百八十九万六千一百二十八.

THE KEY is, we use four digits as a loop for convenience, 千百十万,千百十个. We don't say 七千万五百万八十万九万, actually we omit the anterior units of 万 and hold only one to indicate.

万万 for 10^8 is not used today, commonly. We have 亿. And again, 346,275,896,128 is reading as 三千四百六十二亿七千五百八十九万六千一百二十八.

After that is 兆, the unit you asked. So it means 10^12. Thus, there are 12 zeros behind 一兆, as 1,000,000,000,000.

Here's a different way to show a number bigger than 万, and I think it may be the reason beset you and many people.

"十万为亿,十亿为兆,十兆为京." 亿=100,000, 兆=1,000,000, 京=10,000,000.

Then 75,896,128 is reading as 七京五兆八亿九万六千一百二十八.

The chaos comes, for we don't follow the original rule that each digit has its own unit. We use four digits as loop to reach 100,000,000,000 in the economic region on daily life. With the total amount of GDP in China rising over that much, 兆 will be used as a new current unit in the mainland. And the past problems of the units will still troubled people even then.

  • Although I already understood how numbers are formed, all the background in these answers is interesting and may help others. I did add emphasis to the part that actually answers part of the question.
    – 伟思礼
    Commented Jan 25, 2018 at 3:36
  • @伟思礼 I gave two answers so I emphasized the other one.
    – Hao FU
    Commented Jan 25, 2018 at 4:30


I might had misunderstood the question. I think the OP is askeing '兆' as 'part of' a number(unit), for example 瓦 (MW) . Not '兆' as a number itself, for example "一日圆" is "one trillion yen"


The text below therefore did not answer the original question, but adding additional information on the character 兆 instead


million million (China)

trillion (Taiwan)



Trillion (short scale) = 1,000,000,000,000; one million million; SI prefix: tera-

the current meaning in both American and British English


Trillion (long scale) (1,000,000,000,000,000,000); one million million million; SI prefix: exa-), the former meaning in British English and current usage in many non-English-speaking countries

Since the current meaning of 兆 (trillion) is 'one million million'(China's standard) It should be our standard.

  • Are you saying that CEDICT needs to be changed to also add "(old)" for million and mega? And when you say "our," are you referring to this site, or to some Chinese-speaking country? I have nothing against Cantonese, but I'm currently trying to acquire 普通话. fefe and user3306356 seem to be saying it is more commonly used for "mega"
    – 伟思礼
    Commented Jan 24, 2018 at 6:52
  • 兆 in 兆瓦 (MW) is 'one million' ( 瓦) . But '兆 ' itself as a number means 'trillion'
    – Tang Ho
    Commented Jan 24, 2018 at 9:43
  • @tang ho: the controversial started in ancient time: how to interpret "兆", as 百萬, 萬億 or 億億. this wiki has info: zh.wikipedia.org/zh-hk/兆 Commented Jan 24, 2018 at 10:45

In fact, 兆 could be million, trillion, or 10 quadrillions. In China mainland, the word is usually used to indicate million. Like the sentence "The file is 1MB" could translate to "这个文件(的大小是)一兆"(although, we usually just write "1M" or "1MB" instead of "一兆" since it's simpler). The "兆" in "兆瓦", "兆赫", "兆帕" also means million. But I heard in Taiwan, it usually means trillion.


According to Chinese (mainland) national standard, only the metric prefix "mega-" (for 106) is 兆, while a trillion (1012) should always be 万亿, never 兆.

e.g. 一兆字节 (or 一兆 for short) means one megabyte (1 MB), and 一兆赫 means one megahertz (1 MHz).


10的6次方 兆 M


In Taiwan, most people use 兆 for 1012.

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