Say, you want to write a novella. Novellas are usually between 17,500 and 40,000 words. Let’s go with 30,000.
30,000 / 1,000 = 30 x 3 = 90 / 5 = 18 weeks
If you write 1,000 words a day, allowing additional time for writing and editing by a factor of three and you write five days a week, you can finish a 30,000-word novella in eighteen weeks.