Few of the free calculators helped couples forecast retirement income for a surviving spouse. They rarely let users enter separate information for both spouses and run numbers with differing life expectancies for them, for example. When the calculators recommended annuities for retirement income (most didn't), none suggested buying one with a survivor's benefit. Some of the calculators allow for separate entry of data for each spouse, but even these typically assume that both people retire at the same time. Spousal issues regarding Social Security benefit claims can be complex - beyond the capability of any online calculator.
If you're married, calculate retirement income needs for you and your spouse together and separately, using different life expectancy scenarios. This will help ensure that the one who lives longer won't run out of cash. "Doing the 'what-ifs' can help you see just how differently things can turn out," says Turner.