I am currently writing a teen novel in google docs. Right now, I'm considering a page single spaced. What is the industry standard for what a page is considered?
Generally, a page is anywhere from 250-400 words. Sometimes less, sometimes more. 300 words is a good number if you're trying to estimate how many physical pages your printed novel will be (but keep in mind, physical page count is affected by the size of the page, the size of the text, etc.).
In Google Docs, highlight your text (ctrl+a highlights everything) and click ctrl+shift+c to see your word count. Divide that number by 300 to get, roughly, your page count.
Word count is definitely the "industry standard".