Social Security retirement benefits are calculated based on the average of an individual’s highest 35 years of earnings, adjusted for inflation, according to explanations provided by experts in the field. When a person applies for retirement benefits, the Social Security Administration (SSA) reviews their earnings history and selects the top 35 years to compute the monthly benefit amount. These years do not need to be consecutive, and if an individual has fewer than 35 years of earnings, the remaining years are counted as zero.

Each year’s earnings are indexed to account for inflation, but this indexing varies depending on the beneficiary’s year of birth. For example, someone born in 1964 who earned $20,000 in 1990 would have that figure adjusted by a factor of 3.3, resulting in $66,000 for Social Security calculations. Meanwhile, an individual born in 1959 with the same nominal earnings in 1990 would have those earnings indexed by a factor of 2.5, or $50,000. The SSA provides detailed tables of these indexing factors on its website.

After indexing, the SSA totals the highest 35 years of earnings and divides the sum by 420 (the total number of months in 35 years) to determine the average inflation-adjusted monthly income. The benefit amount is then calculated using a progressive formula that returns a higher percentage of the average income to lower earners. For individuals born in 1964, the formula applies 90% to the first $1,286 of average monthly income, 32% to the next $6,463, and 15% to any remaining amount. These thresholds, known as “bend points,” also vary annually and by birth year.

Beyond the basic benefit calculation, the concept of the “primary insurance amount” (PIA) plays a central role. The PIA represents the foundational retirement benefit calculated at age 62, incorporating earnings up to that age. Subsequent earnings after 62, along with cost-of-living adjustments (COLAs), can modify the PIA. However, earnings after age 60 are not indexed for inflation and are counted in current-dollar terms only. This means that even if an individual continues working full time beyond 62, these post-62 earnings may not substantially increase their benefit because they may not rank among the highest 35 years once inflation adjustments are considered.

This nuance often leads to confusion among beneficiaries, who may notice that their estimated benefit at age 66 is only marginally higher than at 62, reflecting COLAs rather than significant changes from additional earnings. Despite the intricacies of the formula, officials advise most people to rely on the SSA’s online tools to obtain benefit estimates tailored to their personal earnings records. The “Get a benefit estimate” feature on socialsecurity.gov offers users a straightforward way to project their future retirement benefits without needing to navigate the formula’s complexities themselves.