Converter tools
Converting Chinese means four quite different things, and they get confused constantly because the word is the same for all of them. Nothing on this page changes what a text says. Everything on it changes how the text is written down, and picking the right tool is mostly a matter of knowing which of the four you actually want.
The first is romanisation: writing Chinese sounds with Latin letters, or with the symbols used in Taiwan. Pinyin is the standard you will meet almost everywhere, but it is far from the only one ever used, and older books, library catalogues and maps are full of the others. There are tools here to go from characters to pinyin, to go from one romanisation to another, and to write a reading in the International Phonetic Alphabet. Going the other way, from pinyin back to characters, is possible and is offered here, but it guesses: a great many characters share a pronunciation, and only the sentence decides between them.
The second is the script itself: traditional and simplified characters, the two sets in use for the same language on either side of the Taiwan Strait. Converting between them is not a translation and is mostly mechanical, with a few cases where one simplified character stands for several traditional ones and the meaning has to decide. Calligraphy belongs here as well, since rendering your text in seal or cursive script is the same characters written another way.
The third is encoding, and it is a job for a web page rather than for a reader. A character can be written as itself, or as the numeric code a browser understands, and these tools go both ways. If you are pasting Chinese into a page and getting rows of question marks, this is the group you want.
The fourth is input: getting Chinese out of a keyboard that has no Chinese on it. That is what the pinyin keyboard and the online input editor are for, and neither needs anything installed.
Two tools here are not about text at all, and are grouped with the converters because they convert something else. One reads Chinese numbers, which are written on a different principle from ours and have a separate set of characters used on cheques and contracts. The other handles the traditional units of length, weight and area that are still in daily use for food, land and cloth alongside the metric system.