Word Count

Something that I mistakenly did when first starting out (and I see a lot of others do it too) is try to figure out the size and page numbers of my work.

Okay, it's fine if you're just doing it for fun. But don't mention it in query letters.

A) Because loads of things affect the page count. The same novel can be practically any size you want it to be. When they consider your work for publication, they don't want to know your arbitrary page guesstimation. Just give them the word count, and the professionals know what to do from there.

B) It proves that you're a newbie. Not the "I'm not published yet, but I'm willing to work hard to make it happen" kind. But the "I haven't done any research on this stuff because I think I'm already as amazing as J. K. Rowling" kind. The first, people like. The second, they despise. Don't be the second kind.

C) It's a lot more efficient. Saying "My novel is 79,000 words" is just plain better than "In print form, my novel will end up being around 300 pages, depending on font size."

Just a note:

Knowing the word count is also helpful for your own information. You need to know whether your manuscript is even marketable, and there are definite limits to what publishers will accept from a new author.

Keep your manuscript between 50k and 100k. 

Obviously this doesn't include pictures books or easy readers.

These are not hard and fast limits. Every genre has its own acceptable range. Fantasy tends to run much longer than romance, for example. And if you have something really spectacular, exceptions are made. But don't bank on that.

If you do decide to flout the rules, try to be reasonable. 800,000 words is an automatic rejection no matter how good. (This is literally the length of the bible.)

But the best way to get lucky is to do the hard work. Do your research on word counts, and it will pay off.