When calculating annual income for retirement do you use annual income before taxes or after taxes.?

I notice that many online calculators don’t specify(before or after taxes) and I don’t know how that affects the formula.

Public Comments

1. Nobody knows what taxes will be then, so current income and income then would be gross income. A good calculator will attempt to account for inflation and social security then. Likewise if it has input for current expenses it should figure the inflated cost of those expenses. For example I figured I could live on 80% of my income because I am contributing 22% of my gross income to my 401(k). But allowing for inflation, 10 years from I may need the same dollars plus social security to equal the dollars I am living on now. And I will need more per year if I am still around 20-25 years later.
2. I'm not sure if this one helps but it has an after tax field. http://www.retirementcalculators.org/retirement-estate-calculator.php