The percentage of a worker's pre-retirement income that is paid out by a pension program upon retirement. In pension systems where workers get substantially different payouts due to their differing incomes, replacement rate is a common measurement which can be used to determine the effectiveness of the pension system. In some cases, workers can use replacement rates to help estimate what their retirement income might be from the plan.

Replacement rates are commonly mentioned in the debate over the U.S. Social Security system. Under the current Social Security law (as of 2010), replacement rates are at about 45% for the average worker. The replacement rate can allow for individuals to plan for retirement. For example, a worker with pre-retirement income of $100,000 their can estimate their pension at around $45,000 at the current 45% replacement rate.