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system
calculating required rate of return for an income-generating savings account
user
line one shows your 1m, a return with a given rate, and year end withdrawal starting at 25,000.  so line 2 starts with that balance, applies the rate again, and shows the higher withdrawal, by 3%/yr.  in column one, i show the cumulative effect of the 3% inflation, and the last number in this column is the final balance (903k) but divided by the cumulative inflation.  to summarize - if you simply get the return of inflation, and start by spending just that amount, you'll find that after 20 years, you have half your real value.  the 1.029 is a trial and error method, as i don't know how a finance calculator would handle such a payment flow. i can load the sheet somewhere if you'd like.  note: this is not exactly what the op was looking for. if the concept is useful, i'll let it stand. if not, downvotes are welcome and i'll delete.
assistant