how many games before your provisional chess rating matures?

Answer 1

20 in most places.

"A provisional rating usually lasts about 20 games. With the United States Chess Federation, your first rating will be 400 points higher or lower than your first opponent, depending if you won or loss. From there it will taper to 200 for your second, and gradually decrease until it reaches your real rating.

Other sites instead of basing your rating on your first opponent may start you off at 1200 or 1500 for ratings.

If you have other questions on ratings, feel free to ask :) "

Answer 2

it takes 20 rated games,unrated ones do not count.