Accounts are coming
There is nothing to log into yet. Every calculator on Calcbase works without an account, and always will.
What accounts will be for
The plan is to let you save a set of figures across several calculators and see them as one picture. A house, a car and a holiday in the same year is one decision, not three, and no calculator on this site currently treats it that way.
Nothing you enter today is stored, and that will not change for the calculators themselves. An account would be something you opt into, not something you need.