100k / (1 - (0.28[1] + 0.093[2])) = 159,489.
Plus if you retire, you're going to be managing your own health insurance, so the required living expenses number increases, probably by thousands of dollars a year. And it's not like you can flip from a frugal living style to a more flagrant one afterward, so you're going to have to live with room mates for the rest of your life, and never eat out, still.
[1] http://federal-tax-brackets.net/2014-federal-tax-brackets.ht...
More importantly the goal is not necessarily full retirement. Plenty of things are entertaining and make some money. Perhaps you only make 5k/year as a writer or painter well on its own that might not mean much but it can easily boost your nest egg over the next 20 years. Or perhaps teach a class at the local collage or even some of those short training classes. Not to mention long shot’s like trying your hand at acting.
PS: Your expenses often rise as you age but even just working 10 years entitles you to some Social Security benefits.
Granted, Heath issues, dependents, or debt can make this a non starter. But, just because most people you work with spend most of what they make every month means you need to do the same.