You can change all of these variables to whatever works for you.
We start with your target salary of 0 before deductions (tax etc.). Most salaried positions come with some form of benefits (healthcare, pension contributions and more), and we estimate that replacing these would cost about % of that salary. Then, most professional salaried employees would hope for a bonus, again, we assume %. That leaves us with a target of 0 to make.
Of the 365 days in a year, are weekends.
We think you are in The United States of America. As far as we can tell, your country is one of the very few that doesn't mandate holiday time for workers. We do though, so we've given you holiday days - the average of the countries we do have data for.
The average number of unplanned (sick or otherwise) days worldwide is 6.4, but we’ll use to be safe.
Finally, as a freelancer, approximately % of your time is spent on non-billable work, so we take that out of the picture too.
That gives us 0 / days for a day rate of 0. We’d recommend rounding that up to the nearest 5 for the sake of sane accounting.