The 4% rule is a gross portfolio withdrawal idea. Assets under management (AUM) fees come out of the account, so they change both spending power and ending wealth — but not by simply subtracting the fee from 4% (for example, 4% − 1% is not 3%).
Research-style estimates (for example, work popularized by Michael Kitces) suggest a 1% investment expense might reduce a 4% safe withdrawal rate toward about 3.6%, not 3%, because fees shrink when the portfolio shrinks in bad markets. This calculator shows that spending impact — and the much larger effect fees can have on ending wealth when markets are kinder.
Use Simple model for a constant-return estimate, or Sequence scenarios for three teaching paths (tough / typical / favorable). This is not a full historical backtest like FiCalc; it focuses on the fee question.