The U.S. Office of Personnel Management and websites such as FederalRetirement.net offer a variety of tools for managing annuities of a federal retirement fund. These tools include calculators for Civil Service Retirement System and Federal Employee Retirement System annuities as well as conversion charts for any leave time taken, according to the Federal Retirement Network.
The original federal retirement program was the Civil Service Retirement System. It is similar to a pension and was expanded in 1987 with the Federal Employee Retirement System, says the U.S. Office of Personnel Management.
The FERS is a three-tiered program that provides income from three different sources: a basic benefit plan, Social Security and the thrift savings plan, reports the U.S. Office of Personnel Management. Like a 401(k), the latter two can be moved to any new job outside the federal government, while the basic benefit plan is for government employees only. Basic benefits and Social Security payments are taken out of each paycheck, while a thrift savings plan account is set up by the agency that employs an individual, and it receives 1 percent of an employee's gross pay each pay period.
A CSRS annuity is calculated using length of service and pay. Overtime, allowances and other pay are not included in the calculation, says the Federal Retirement Network. Eliminating the fractional parts of any month, the total annuity cannot be more than 80 percent of the average pay unless unused sick leave is credited toward it.