Page count is a function of font type, font size, margins, line spacing and paragraph structure. And college students learned decades ago how to lengthen their papers by even slightly changing those variables. 
If you want to make a rough estimate based on word count, then determine for yourself what fills a page using your defaults, then just do a word count. (Or use an app which does the calculations for you based on your settings.)
FYI character counts are used in publishing to accurately determine the page count of a book or magazine article. Word counts are only approximate, because words vary in length, and because the space(s) between words vary in number. Character counts tell you precisely how much real estate a piece of writing will occupy.