Word Counter Plus
Word Counter Plus is a simple and useful tool that lets you views stats on selected text. Simply highlight some text on a webpage, right click on it, and select the Word Counter Plus menu item. It will tell you the number of words and characters selected as well as the average and longest word length. Unlike similar word counting extensions, this one does not open an external webpage just to do the counting, nor does it require any permissions.
You can install this Chrome Extension here.