From the USA.gov Blog:
Whether you’re getting close to retirement or planning for the future, check out Social Security’s retirement estimator.
The estimator gives you an idea of what your monthly Social Security benefits would be, based on your current record of Social Security earnings. Your actual benefit amount cannot be determined until you apply for benefits.
As you plan for your retirement, keep in mind that you’ll need about 70 percent of your pre-retirement earnings to maintain your standard of living. Social Security benefits will only make up a part of this percentage and should be supplemented by a pension, savings, and/or investments. Check out 10 Ways to Prepare for Retirement.