The Heritage calculator also shows how large a retirement nest egg that a worker could have generated by investing those same payroll taxes in an individual retirement account.
Most calculators ignore the amount of payroll taxes paid into the system altogether.
This element, combined with the alternative investment feature, often produces surprising results, Beach said. At least the Ann Arbor woman can look forward to getting back more from Social Security than she paid in. The Heritage calculator provides a more reliable estimate in part because it relies so heavily on the Social Security Administration's own data and future income projections. By contrast, the SSA calculator allows an individual to enter his or her occupation, a far less reliable measure of life expectancy, he said. Besides age, gender and location, they can enter their own exact current and past earnings, as well as their expected retirement age and details from actual investment portfolios.