Online financial-planning tools have a habit of spitting out terrifying numbers when people use them to figure out how much to save for retirement. Most tools, from the AARP’s to the Social Security Administration’s, yield similar answers when one enters spending estimates, expected salary increases, and assets: They tend to advise their users (most of whom are workers in their 40s or 50s) to have 10 times the amount of their salary in savings before they retire. It’s a cutoff that some economists claim is too high, but it’s actually quite realistic—and presents a good argument for saving aggressively.

Ten times most people’s salaries is usually a lot higher than what they have saved up. First, more than half of workers don’t have more than a few thousand dollars saved up in retirement accounts. And by the time the average professional is between the ages of 50 and 64, his or her household has accumulated about $181,000 in 401(k) and IRA accounts. That’s only 10 times their salaries if they’re earning below the poverty line.