Although I like online retirement calculators, they can’t tell you everything. There are a handful of wild cards that could mess you up.

When figuring out how much you need to retire, you need to know two basic facts: 1) How much you need based on your current/projected lifestyle spending and 2) how much you’re able to save, based on some conservative investment returns.

Of course, you can plug in the numbers and hope for the best. You can scale back your lifestyle by downsizing or move to a state with a lower cost of living. Yet there are always some items that can throw off your assumptions that the calculators can’t predict.