For example, go to a tool like T. Rowe Price's Retirement Income Calculator, plug in a $ 1 million portfolio and assume an initial 4 %, or $ 40,000, withdrawal that will subsequently be adjusted by the
inflation rate, and the calculator will estimate that there's roughly an 80 % chance that your nest egg will be able to sustain that
level of withdrawals for
at least 30 years, or, if you retire
at 65, until you reach age 95, a
reasonable planning assumption given today's long lifespans.