Minimum sample size for moderation analysis

Hi everyone,

And thanks for the great job you are doing here. I have a question regarding statistical power and regression.
How can I calculate the minimum sample size based on the number of moderators I have in multiple regression?
Is there an online tool for this?
If for example I have 5 independent variables and 3 moderators, what is the minimum sample size I should obtain?

Thanks a lot in advance!