Here's a tip from CNBC:

You can head to Retirement Estimator on the Social Security Administration's website for a ballpark estimate. Enter some basic information—your name, Social Security number, date of birth, mother's maiden name and last year's income—and the tool will calculate your benefits based on your earnings history. You'll get estimates for the amount you'll receive if you take your benefits early—at age 62.  Another estimate for benefits at your full retirement age—whether it's 65, 66, or 67—and you can also find out the maximum benefit you'll receive if you wait until age 70.