ok, so around 16h after the last block that brang you to 100% fill bar ( but you have to know it ! ) seems to be the only way.
Well no, you could be at 99% and have all 99% confirmed.
But 16h after you hit 100% is the longest it could take.
Well it could be 17-18 hours due to a long period of not finding blocks solved, but 16 hours is a pretty good guestimate as it will be just a little bit longer than that if everything played out right and every block was solved at exactly 10 minutes.