If you track your spending, I don't think you need a retirement calculator. Like Spartana, if you know how much you need and want (discretionary) to spend in a month, it's pretty easy to figure it out. For example, using 4% as my safe withdrawal rate, which can be adjusted a bit in response to the market, I figured I wanted a certain amount per month from my savings on top of pension and other income. In my case, we reached the savings amount that gave us the target monthly SWR and retired.
I like Mathjak's cautious and sensible approach. I am reminded of friends and family who are struggling to get by because they failed to save enough money. My heart goes out to them, whatever caused the situation.