Scaling issues
Great but with some math issues
For example, starting with a 1,000,000 balance, a 5% rate of return, and 3% inflation adjustment. It should be possible to withdraw inflation adjusted 20,000 each year (2% of each years balance) while still allowing the principal to grow with the inflation rate.
However the calculator claims that the balance will reach 0 after 159 years. It will actually be a staggering 110 million dollars after 159 years.