This extension shows how many characters are in a selection. It will also convert between ASCII (char), ASCII (int), & 8-bit (Byte).
This extension is fairly simple, straight-forward, and self-explanatory (if not, please let me know what I can do to enhance it).
In version 2 you can now change what format the source string is in (i.e., the string to be converted, in the top input box). Source options are the same as the conversion output options; ASCII(char), ASCII(int), and Binary. The 'Convert' link will then cycle through the 3 conversions.
Character Counts is open-sourced on GitHub (feel free to make a PR for adding something useful).
* GitHub: https://github.com/KDCinfo/character-counts