All depends on size and where in kidney. Could take a few days or a month or more. The stone isn't always moving
If the stone is in the low part of the kidney, a suggestion would to be to drink 1-2 cups of water, wait 1/2 to 45 minutes then lay on your side with the kidney w/ the stone in the air.
The best way is to drink a lot of water 8-10 cups a day.
unfortunately the little buggers can be painful.
Sometimes they pass and you will not even know it!
I had stones in both kidneys in Aug 07. (more in left ) A year later, the one in the right was gone & I have no idea when it passed.