You will see different methods for calculating savings rates. It doesn't really matter, as long as you are consistent. I do include principal payments on debt. Here is my formula:
(Savings + debt principal paid + retirement contributions)/(Take-home income + retirement contributions)
Congrats on killing the CC debt!
This method lets payroll deducted expenses like medical insurance, FSAs, disability insurance, life insurance, etc slide under the radar. Additionally I don't count principal reductions on any debt that isn't a mortgaged asset as savings. So no go on student loans or credit card principal reductions counting as anything other than an expense. I wouldn't count car either.
I do:
(Savings + mortgage principal paid + retirement contributions + employer 401k match, profit sharing, free HSA money, etc)/(Gross Salary - FICA Taxes - Federal Taxes - State Taxes + employer 401k match, profit sharing, free HSA money, etc)
Added bonus that this method forces you to learn how to calculate your own federal taxes.