Go to a retirement income calculator that uses Monte Carl0 analysis to
make projections, plug in such information as your age, salary, savings rate, the amount, if any, you already have stashed in retirement accounts, the stocks - bonds mix you arrived at in step 2, the age at which you intend to retire, the percentage of pre-retirement income you'll require in retirement (80 % or so is a
decent estimate) and how many years you expect to live in retirement (I suggest to age 95 to be on the conservative side)... and voila!