Here you can find approximately how much time you need to run your tournaments as well as a calculator to help determine payouts.
docs.scoreholio.com
However you need to also estimate how fast the players play, are they good players, bad players, drunk players, stoned players, do they all smoke, do they chat and go to the bar after every other shot, etc...
Really you just need to get the number of rounds it takes to get through the field after every set. If you have enough tables for everyone to play on, then it's easy. If not, then you need to do a bit of math for the first rounds to see how much it will take to get through those to get to where every match can be on a table soon as they are done without waiting.
You can get the number of rounds it will take here
https://www.printyourbrackets.com/double-elimination-tournament-brackets.html
So a 16 player tournament, with 8 tables, double elimination will take 7 rounds, multiply that by how long a match takes and you get the tournament length. If you have say 3 tables, now you need to add a few extra rounds to that for waiting.
It's harder to sort out the exact math than to do some logical mind estimating.
I know events I play in that get say 8-16 players of mostly B level, it takes like 4 hours for a race to 5 on the low end and about 7 hours on the high end of players without any waiting for tables.