Tens of millions of older Americans rely on Social Security today, and for many it is the backbone of their retirement income. Social Security is not designed to cover all of your retirement expenses. According to the SSA, benefits are intended to replace about 40% of your pre-retirement income, leaving a significant gap that must be filled from other sources. Understanding how the benefit formula actually works gives workers a real edge in maximizing what they collect once they stop working.
One Reddit poster in the r/ChubbyFIRE community recently raised a question that resonates with a wide range of pre-retirees: after logging into SSA.gov for the first time and finding 20 years of contributions on record, they wanted to know what another decade of work would actually do for their monthly check. The answer is: quite a lot. And grasping the mechanics behind it matters for virtually everyone still in the workforce.
How Social Security benefits are calculated
Social Security calculates retirement benefits based on your 35 highest-paid years of earnings, each adjusted upward to account for changes in national wages over time. The SSA first considers a beneficiary’s 35 highest-earning years, with each year’s earnings adjusted for national wage growth, to determine average indexed monthly earnings (AIME). SSA then runs this AIME through a progressive replacement-rate formula to determine a beneficiary’s primary insurance amount (PIA), the monthly benefit received if the worker elects to start benefits at full retirement age.
The earnings cap is an important wrinkle for higher earners. The PIA formula is based on AIME in your 35 highest-earning years after age 21, up to the Social Security wage base. In 2025, that base is $176,100. The wage base is the maximum amount of income on which Social Security taxes must be paid. Workers who earn above that threshold in a given year do not pay Social Security tax on the excess, and those dollars above the cap are not counted in the benefit calculation either.
With only 20 years of contributions on record, the Reddit poster’s benefit estimate still has substantial room to grow. The SSA bases retirement benefits on the highest 35 years of earnings and the age at which benefits start. Stopping work before reaching 35 years of earnings affects the benefit amount: a zero is used for each year without earnings in the calculation, and years with no earnings reduce the retirement benefit amount. So every additional year of work at a solid wage does two things at once: it fills a zero-year slot and may replace an earlier, lower-earning year.
The wage-indexing piece is also worth understanding clearly. A $50,000 salary earned 20 years ago is not treated the same as $50,000 earned today. Earnings are indexed for inflation, so earnings from years past are not compared to current-year earnings at face value. The older earnings are adjusted upward to account for wage growth over time. That means early-career years can count more toward the final benefit than workers expect after indexing is applied.
Once a worker has more than 35 years of earnings, the formula simply keeps the 35 highest-indexed years and discards the rest. Higher-earning years will replace lower-earning years in the calculation, but only up to 35 years total. If a worker has more than 35 years on record, only the highest 35 count. Continuing to work at higher pay can replace earlier lower-earning years in the calculation, potentially increasing the benefit.
Keep tabs on your earnings and benefits
Because the benefit estimate on SSA.gov incorporates assumptions about future earnings, accuracy improves the closer you get to retirement. The estimated average monthly Social Security retirement benefit for January 2026 is $2,071. That average, however, masks a wide range: some retirees with lower lifetime earnings may receive closer to $900 to $1,000 per month, while the highest earners who delayed claiming until age 70 could see monthly payments approaching $5,108, the absolute maximum for 2025. Checking your SSA.gov account annually keeps you informed of where you stand and, just as importantly, catches any missing wage data before it shrinks your benefit at retirement.
An often-overlooked reason to do that annual review is accuracy. Employers occasionally fail to report wages correctly, and Social Security has no way to credit you for earnings it never recorded. Spotting a discrepancy early and getting it corrected is far easier than trying to reconstruct decades-old payroll records after the fact. Your most recent Social Security statement will list every year of covered earnings, making it straightforward to compare against your own tax records.
Filing age adds another powerful lever on top of earnings history. Workers born in 1960 or later reach full retirement age (FRA) at 67. Claiming at 62, the earliest option, permanently reduces monthly checks. For every month from FRA until age 70 that a worker postpones filing, Social Security increases the eventual benefit by two-thirds of 1%. Those who delay from age 67 all the way to 70 receive an extra 24% added to their monthly payment. That 24% boost stacks on top of whatever the earnings-history calculation produces, making the delay question one of the most consequential choices in retirement planning.
A financial advisor can run the numbers on your specific earnings history, health outlook, and other income sources to identify the claiming age that makes the most sense. The conversation is worth having well before retirement, when there is still time to build savings around a realistic benefit projection. Then, as retirement approaches and the SSA estimate becomes more precise, a follow-up session can fine-tune the strategy around your actual expenses, savings balance, and any pension or investment income you expect to draw.
Editor’s note: This update added the 2025 Social Security wage base of $176,100, the average retiree benefit of roughly $2,071 per month as of January 2026, the maximum benefit of $5,108 per month for top earners claiming at age 70 in 2025, and the 24% delayed-retirement-credit bonus available to workers born in 1960 or later who defer claiming from FRA to age 70.
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