Formula
Your IPERS retirement benefit is calculated using this formula:
Your average salary x a multiplier based on the number of years you work in IPERS-covered employment minus a reduction if you retire before your normal retirement age.
Average salary
This is the average of your highest five years' salaries. These don't have to be the five years that immediately precede your retirement.
Multiplier
This increases two percentage points each year you work in IPERS' covered employment up to year 30. From year 31 to 35, the multiplier increases on percentage point each year. The maximum multiplier is 65% at 35 years in covered employment.
At retirement you may "purchase service" - or buy work time - to increase your multiplier.
Reduction
A reduction is applied if you retire before you reach a normal retirement age. IPERS will reduce your retirement benefit by 0.5% for each month (or 6% annually) that you receive retirement benefits before age 65.