Vim has a built in shortcut for counting words. To see the word count for the whole buffer type:
You will see something like:
Col 11 of 54; Line 12 of 24; Word 39 of 68; Byte 360 of 727
Meaning we are currently at word 39 and the whole buffer contains 68 words.
To see the word count for a selection, first select and type the same shortcut
g<CTRL-g> the result should look something like this:
Selected 7 of 24 Lines; 23 of 68 Words; 234 of 727 Bytes
in this case I have selected 23 words.