The Chinese Number Conversion Perl module used above to convert between Chinese character numbers and Arabic numbers is available for download.
While China has for many uses adopted the Arabic numeral system familiar around the world, it also still uses its native Chinese character number system. The Chinese system is also a base-10 system, but has important differences in the way the numbers are represented. Chinese has characters for numbers 0 through 9, as seen above. In addition to the character shown above for zero, a simple circle is also used. Pronunciation for the characters uses the standard Romanization scheme in China called "pinyin". The number at the end of the pinyin indicates the tone.
Eleven in Chinese is "ten one". Twelve is "ten two", and so on. Twenty is "Two ten", twenty-one is "two ten one" (2*10 + 1), and so on up to 99. One-hundred is "one hundred". One-hundred and one is "one hundred zero one". One hundred and eleven is "one hundred one ten one". Notice that for eleven alone, you only need "ten one" and not "one ten one", but when used in a larger number (such as 111), you must add the extra "one". One thousand and above is done in a similar fashion, where you say how many thousands you have, then how many hundreds, tens, and ones. An exception to this is for zeroes. When a zero occurs in the number (except at the end), you need to say "zero", but only once for two or more consecutive zeroes. So one-thousand and one would be "one thousand zero one", where zero stands in for the hundreds and tens places. Try different numbers in the converter above to practice and check on other numbers.
What is different from American English is that when you get to ten-thousand, Chinese has its own word (wan4), unlike English where you must use a compound of ten and thousand. Only after ten thousand does Chinese start using compounds itself. One-hundred thousand is "one ten wan4" (where wan4 is the Chinese word for ten-thousand that English lacks). Chinese goes on like this until 100 million (yi4), where it introduces a new character. This happens every four decimal places, unlike American English where it happens every three decimal places (thousand, million, billion, trillion, etc. are all separated by three decimal places).
Regular Chinese characters for numbers use relatively few strokes. The characters for one, two, and three are just one, two and three parallel horizontal strokes, respectively. To prevent fraud when writing checks and other cases where fraud is possible, Chinese also uses a series of more complex characters for the numbers. It is easy to change a "one" into a "two" in regular characters, but with the formal complex characters, this is impossible. See above for a listing of the equivalent formal characters.
As in English, one can also abbreviate a number by just listing the digits with the tens, hundreds, thousands, etc. omitted (as the web counter below does).
When talking about amounts, sometimes a variant of two is used in the hundred-million, ten-thousand, thousand, or hundreds place: (liang3). It is never used in the tens place. Sometimes when used as an amount it can also replace two alone.
Shorthand characters also exist for twenty and thirty and are often used in newspapers, especially in dates. These are (nian4) for twenty and (sa4) for thirty.
To express fractions and percents, Chinese uses the denominator followed by the two characters (fen1 zhi1, "parts of"), followed by the numerator. So two-thirds would be "three fen1zhi1 two". In the case of percents, you would say "hundred fen1zhi1 amount", e.g. the way to say 63% is "hundred fen1zhi1 six ten three". When used in percents, just say hundred and not "one hundred".
The decimal point is expressed with the character (dian3).