I do a lot of work online and for a while I didn't have a word processing program on my laptop, since it is such a basic model. So, I used an online word count website to calculate it. People often need an accurate word count, because articles are usually expected to be a certain size.
You can also set up your browser so it will do spelling checks and word counts and so forth if you want it to.
I have OpenOffice installed on my computer now, but I still like having the browser function set to that, because it's much easier than copying and pasting my work between different places.