The Social Security Retirement Calculator offered by Financial Engines does the best job of the free calculators because it actually considers a number of claiming strategies and clearly identifies the one that maximizes the benefit for the family and not just the individual.
The best way to use the AARP’s Social Security Benefits Calculator is to have your estimated monthly Social Security benefit to input into the software. Then the software spits out some useful estimates and even calculates what percent of your retirement needs your monthly benefit will cover.
The Social Security Administration's Retirement Estimator is the place to start to get your actual Social Security earnings record and estimated monthly benefit. The tool provides a benefit estimate for three claiming ages: age 62, your full retirement age, and age 70. You can play What-if simulations with future income and select alternative ages to stop working and examine how that changes the amount of you will receive from Social Security. The calculator does not take spousal benefits into account or make recommendations about the best age to claim. The tool is restricted to people who have enough credits to retire for benefits but have not yet filed a claim.
The Consumer Financial Protection Bureau’s Planning for Retirement provides a rudimentary estimate of your monthly or annual Social Security payments at various claiming ages. Since the tool does not use actual earnings, it is at best an estimate. Still, it’s a quick way to look at the impact of claiming or delaying benefits.
The Center for Retirement Research at Boston College's Target Your Retirement calculator literally talks you through the tool. In addition to estimating your social security retirement benefits, it considers any pensions, equity in your home, lifestyle changes, and spending habits. It doesn’t make any claiming recommendations.