We unpubbed writers are obsessed with word counts. We are terrified we are going to be too short or too long. How do publishers and agents figure this out? It should be fairly simple, but its not. There is the basic formula of page # x 250. This is based on a ms written in Courier 12 with exactly 25 lines per page. This formula doesn't work if you are writing in TNR 12. There was a formula for that as well, but I forgot it. I do have some other very complicated formulas that takes multiplying my character count with some other number. I'm sure it has something to do with the rings around Saturn. Then there is the computer word count. Which do you go with?
For example, my current WIP is 64750 words using the page # x 250 formula. The computer word count is 10K words less. That is a significant number or is it? I write single title, so I'm not too worried. No doubt an editor will ger ahold of it and decide what they want to do. I shoot for 100K words. If I go by the formula, my computer word count is about 20K less. To be honest, I'm going to use the number that will hold the most advantage for me.
Word count is the least of your worries if you are writing single title. Obviously you need to be concerned if your book is 500 pages. It might be a bit too long, no matter what formula you are using. But for the most part, what those words say is by far more important.