How much should you have saved for retirement? There's actually a simple answer to that. You'll need to start with a bunch of basic assumptions, but all you really need to know is your income and your age.

Let's take a look at hypothetical Joe, who is hired straight out of college. By the time he's 25 years old, he's making $40,000 a year. He should have $4,000 socked away in his retirement fund if he wants to retire at age 65.

How you can get there: Make sure you're contributing enough to your 401(k) to get the full match from your employer.