How much would I have to pay in taxes at age sixty if I cash out my 401k ?

You will pay ordinary income tax on the withdrawal, so the amount of tax you pay depends on your tax bracket, which in turn is dependent on your total adjusted gross income (which will include the amount of the withdrawal), plus other factors such as your filing status, number of dependents, amount of deductions, etc. So it's impossible for us to say withou a lot more infrmation. However, the plan administartor will automatically withhold 20% from your withdrawal for income tax. You should try to figure out whether this amount is too much or tool little, and if necessary plan on filing an estimated income tax payment to make sure you don't underpay - otherwise next April you may owe Uncle Sam interest if there is an underpayment. Also, if you live in a state with income tax that includes taxes on 401(k) distributions, you will owe that as well.