This is a simple and easy-to-use tool to quickly count the number of Chinese characters and number of unique characters (called "distinguishable characters" for some reason). It can add up several counts and will display some other information, but the strength of this tool is its simplicity. It can also quickly deal with large chunks of text (I've tried pasting entire novels and it spits out the result almost instantly). You can also download and run the application locally if you need to!