This is pretty much it. Let’s say at 50 you’re comfortable living off of 4% of your assets, which should have a reasonably high chance of providing income throughout your retirement without depleting your principal. This 4% is assuming 7% market returns before 3% inflation.

How much are you willing to live off as income? If you need $40,000/yr (before taxes) you’ll require $1m in savings. $60,000 requires $1.5m. Tax-advantaged savings like a Roth IRA improve things here a bit but we can ignore it for a general ballpark idea.

Let’s say you’re frugal and only need $40,000. You’ll have to save up $1,000,000 in invested assets over a decade. Given expected 4% inflation-adjusted returns, this works out to around $85,000 in savings each year (adjusted upward 3% each year for inflation).

In order to afford those savings, after tax and $40,000 in annual expenses, I’d guesstimate you’ll likely need somewhere in the ballpark of $150,000/yr of income. Again, adjusted upward 3% every year for inflation.

By the same math, if you want to live off $80,000 a year, you’ll probably need to earn $350,000 or more annually over that decade. The number more than doubles because of the increased taxes at those kinds of incomes.