However, to truly determine logical personal retirement savings goals, you should consider your current expenses, how you expect those to change during retirement, your return on retirement investments, and how long you expect to live. For example, if you just started to save and have 20 years until retirement, you could max out both a Roth IRA and a 401k every year until you retire to meet your goal. When you use a retirement calculator to project how much you need to save, you may have to pick the age at which you plan to retire and estimate how fast your money will grow.