To estimate the number of words in a book, multiply the number of pages by 250. For example, a 400-page book contains approximately 100,000 words.
For a more accurate estimate of the book's word count, choose a random page and count the number of words in the first line. Multiply this by the number of lines on the page to estimate how many words are on the page. Multiply this number by the number of pages in the book. Repeat this process with two other random pages. Calculate the average of the three numbers.
Microsoft Word calculates the exact amount of words contained in an electronic book.