How to account for rehab time lost on Rental Income Calculator

[Tobey Grey]

I'm working on rehabbing my first buy and hold property, a SFH home with a 2 car garage I plan to eventually turn into a studio once the house is done and rented. I am trying to act as my own General Contractor and while I'm saving money this route, it's taking much longer than I anticipated. I would like to calculate the tipping point for when money saved is less than the loss of rental income due to time creep.

I'm struggling to find a calculator that accounts for the lost rental income by month during the initial rehab. Any suggestions for how to calculate this with the Bigger Pockets calculator, or a separate tool?