Once a symbol of extravagant wealth, $1 million is now the retirement-savings goal for millions of Americans.

For retirees able to accumulate $1 million in savings, the funds translate into inflation-adjusted income of $40,000 in the first year of a three-decade retirement using the 4% spending rule. With the addition of the average annual Social Security payment for retirees of about $20,000, a $1 million nest egg can replace about 85% of a $70,000 median household income.