Sure. Actual load calculations use the load calculation form. Here are examples of it.
Residential Calculations
https://www.ladbs.org/docs/default-...oad-calculation-form-in-form-00.pdf?sfvrsn=16
Electrical Load Calculations for Residential Panel - Online Load Calculator
They are much more based on the appliances you have in the house and what types they are and how many rooms of lighting circuits and convenience outlet circuits you have, scaled by the square footage in the house (which you made no mention of),
Your method seemed to be doing something else just by number of breakers in the panel, without even listing these things about what kinds of electrical loads are in the house.
Going through the NEC load calculation in those forms I linked to above will show a number of amps, which does then need to fit within the main breaker for the main electrical service line into the house. And that can tell you if you have any margin of some number of amps available, to add a new circuit for something.