I use Excel often, and have several retirement spreadsheets that I play around with. These calculators though are nice because they also take into account future interest during retirement, inflation rate, etc., so in theory they would be more accurate. And this is one of the only calculators I have found that actually lets you break down your retirement income into that coming from SS, from pensions or investments, etc. For example, if I retire today, but I don't plan to draw SS for 5 more years, and I know how much my yearly expenses will be, it will calculate drawing down only pension/investment income in the first five years, then when SS kicks in, it will divide that income among SS and the pension/investment income, to arrive at the needed yearly expense amount. It really is nice....if only the SS portion were accurate. I even tried putting in that my SS income would be zero, yet it still comes up including SS, which I assume it is calculating from my yearly salary figures that I entered up front. Oh well...I've tried everything...no luck.