I don't have a number, and I believe it's not the greatest target to shoot at for retirement security. I'm a believer in a retirement income goal being the most important measure, To get there, first decide how much is the minimum you want to leave as inheritance or charitable gift when you (or you and a spouse) die. Set that aside, probably physically in a different account, and then anything left over at the "endpoint" from the below gets added to your bequest. Then, solve for what kind of retirement you want:
Let's use a round numbers example - say you want $100,000 pre-tax at today's value per year to live on (multiply as many times as you ingrates want). You may or may not have a paid off house, or a low-interest mortgage. Consider your income sources, which may look something like this:
- Social Security: $30,000 for you, $20,000 for your spouse
- Pension Income: $25,000 per year for one of you (the other had no pension)
- IRA of $1,000,000, for which a safe withdrawal rate is 4%, equals $40,000 per year income (fully-taxable).
That means you have $115k to live on the first year. Throw any remainder in an after-tax brokerage account each year and invest moderately aggressive.
Inflate this by whatever factor you want to use for inflation (3-4%???), and you might be fine with COLAs and maybe some continued IRA and after-tax brokerage portfolio outperformance (?), and you're likely gonna be OK through retirement. If you hit a rough spot, consider selling the house, or raiding the inheritance fund if you are gonna starve, or not get the latest Lamborghini you want. It's your money, after all.
The only guarantee I've made the future heirs is that they will not have to financially support us in our old age.